userland: search and exec tools, spawn library (T14)

rg (ripgrep 15.2), grep (ours, on ripgrep's regex crates), find and xargs (ours), sed (uutils 0.3 wrapper), diff and cmp (uutils diffutils 0.6 with -r), fd 10.5, jaq 2.3, env and timeout. userland/spawn is a small Command-like client of the process interface. search-test.nu: 42 cases match native tools.
2026-11-06 17:21:51 +00:00
parent 665b8a2a03
commit b9e3e3677d
214 changed files with 58132 additions and 45 deletions
@@ -0,0 +1 @@
+{"v":1}
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "815ed7d8de89a236e5f636749f80a5b061017521"
+  },
+  "path_in_vcs": ""
+}
@@ -0,0 +1,100 @@
+name: GnuComment
+
+on:
+  workflow_run:
+    workflows: ["GnuTests"]
+    types:
+      - completed
+
+permissions: {}
+
+jobs:
+  post-comment:
+    permissions:
+      actions: read  #  to list workflow runs artifacts
+      pull-requests: write  #  to comment on pr
+
+    runs-on: ubuntu-latest
+    if: >
+      github.event.workflow_run.event == 'pull_request'
+    steps:
+      - name: 'Download artifact'
+        uses: actions/github-script@v9
+        with:
+          script: |
+            // List all artifacts from GnuTests
+            var artifacts = await github.rest.actions.listWorkflowRunArtifacts({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              run_id: ${{ github.event.workflow_run.id }},
+            });
+
+            // Download the "comment" artifact, which contains a PR number (NR) and result.txt
+            var matchArtifact = artifacts.data.artifacts.filter((artifact) => {
+              return artifact.name == "comment"
+            })[0];
+
+            if (!matchArtifact) {
+              console.log('No comment artifact found');
+              return;
+            }
+
+            var download = await github.rest.actions.downloadArtifact({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              artifact_id: matchArtifact.id,
+              archive_format: 'zip',
+            });
+            var fs = require('fs');
+            fs.writeFileSync('${{ github.workspace }}/comment.zip', Buffer.from(download.data));
+
+      - run: unzip comment.zip || echo "Failed to unzip comment artifact"
+
+      - name: 'Comment on PR'
+        uses: actions/github-script@v9
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            var fs = require('fs');
+
+            // Check if files exist
+            if (!fs.existsSync('./NR')) {
+              console.log('No NR file found, skipping comment');
+              return;
+            }
+            if (!fs.existsSync('./result.txt')) {
+              console.log('No result.txt file found, skipping comment');
+              return;
+            }
+
+            var issue_number = Number(fs.readFileSync('./NR'));
+            var content = fs.readFileSync('./result.txt');
+
+            if (content.toString().trim().length > 7) { // 7 because we have backquote + \n
+              // Update existing comment if present, otherwise create a new one
+              var marker = '<!-- gnu-tests-bot -->';
+              var body = marker + '\nGNU diffutils testsuite comparison:\n```\n' + content + '```';
+              var comments = await github.rest.issues.listComments({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: issue_number,
+              });
+              var existing = comments.data.filter(c => c.body.includes(marker))[0];
+              if (existing) {
+                await github.rest.issues.updateComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  comment_id: existing.id,
+                  body: body,
+                });
+              } else {
+                await github.rest.issues.createComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: issue_number,
+                  body: body,
+                });
+              }
+            } else {
+              console.log('Comment content too short, skipping');
+            }
@@ -0,0 +1,257 @@
+name: GnuTests
+
+# Run GNU diffutils testsuite against the Rust diffutils implementation
+# and compare results against the main branch to catch regressions
+
+on:
+  pull_request:
+  push:
+    branches:
+      - '*'
+
+permissions:
+  contents: write # Publish diffutils instead of discarding
+
+# End the current execution if there is a new changeset in the PR
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
+env:
+  DEFAULT_BRANCH: ${{ github.event.repository.default_branch }}
+  TEST_FULL_SUMMARY_FILE: 'diffutils-gnu-full-result.json'
+
+jobs:
+  native:
+    name: Run GNU diffutils testsuite
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - uses: Swatinem/rust-cache@v2
+
+      ### Build
+      - name: Build Rust diffutils binary
+        shell: bash
+        run: |
+          ## Build Rust diffutils binary
+          cargo build --config=profile.release.strip=true --profile=release
+          zstd -19 target/release/diffutils -o diffutils-x86_64-unknown-linux-gnu.zst
+
+      - name: Publish latest commit
+        uses: softprops/action-gh-release@v3
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        with:
+          tag_name: latest-commit
+          body: |
+            commit: ${{ github.sha }}
+          draft: false
+          prerelease: true
+          files: |
+            diffutils-x86_64-unknown-linux-gnu.zst
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      ### Run tests
+      - name: Run GNU diffutils testsuite
+        shell: bash
+        run: |
+          ## Run GNU diffutils testsuite
+          # Exit code 1 means some tests failed, which is expected and handled
+          # by the comparison below; 2 means the suite couldn't be run at all
+          # 'shell: bash' runs with -e, so don't let the expected exit code 1
+          # abort the step before the exit code is inspected
+          result=0
+          ./tests/run-upstream-testsuite.sh release || result=$?
+          if [[ $result -ge 2 ]]; then
+            echo "::error ::The GNU testsuite could not be run (exit code $result); see the log above"
+            exit 1
+          fi
+        env:
+          TERM: xterm
+
+      - name: Upload full json results
+        uses: actions/upload-artifact@v7
+        with:
+          name: diffutils-gnu-full-result
+          path: tests/test-results.json
+          if-no-files-found: warn
+
+  aggregate:
+    needs: [native]
+    permissions:
+      actions: read
+      contents: read
+      pull-requests: read
+    name: Aggregate GNU test results
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Initialize workflow variables
+        id: vars
+        shell: bash
+        run: |
+          ## VARs setup
+          outputs() { step_id="${{ github.action }}"; for var in "$@" ; do echo steps.${step_id}.outputs.${var}="${!var}"; echo "${var}=${!var}" >> $GITHUB_OUTPUT; done; }
+
+          TEST_SUMMARY_FILE='diffutils-gnu-result.json'
+          outputs TEST_SUMMARY_FILE
+
+      - name: Checkout code
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - name: Retrieve reference artifacts
+        uses: dawidd6/action-download-artifact@v27
+        continue-on-error: true
+        with:
+          workflow: GnuTests.yml
+          branch: "${{ env.DEFAULT_BRANCH }}"
+          workflow_conclusion: completed
+          path: "reference"
+          if_no_artifact_found: warn
+
+      - name: Download full json results
+        uses: actions/download-artifact@v8
+        with:
+          name: diffutils-gnu-full-result
+          path: results
+
+      - name: Extract/summarize testing info
+        id: summary
+        shell: bash
+        run: |
+          ## Extract/summarize testing info
+          outputs() { step_id="${{ github.action }}"; for var in "$@" ; do echo steps.${step_id}.outputs.${var}="${!var}"; echo "${var}=${!var}" >> $GITHUB_OUTPUT; done; }
+
+          RESULT_FILE="results/test-results.json"
+          if [[ ! -f "$RESULT_FILE" ]]; then
+            echo "::error ::Missing test results at $RESULT_FILE"
+            exit 1
+          fi
+
+          if ! jq -e . "$RESULT_FILE" > /dev/null; then
+            echo "::error ::Test results at $RESULT_FILE are not valid JSON"
+            exit 1
+          fi
+
+          TOTAL=$(jq '[.tests[]] | length' "$RESULT_FILE")
+          PASS=$(jq '[.tests[] | select(.result=="PASS")] | length' "$RESULT_FILE")
+          FAIL=$(jq '[.tests[] | select(.result=="FAIL")] | length' "$RESULT_FILE")
+          SKIP=$(jq '[.tests[] | select(.result=="SKIP")] | length' "$RESULT_FILE")
+          ERROR=0
+
+          if [[ "$TOTAL" -eq 0 ]]; then
+            echo "::error ::No test was run; refusing to report or compare an empty test run"
+            exit 1
+          fi
+
+          output="GNU diffutils tests summary = TOTAL: $TOTAL / PASS: $PASS / FAIL: $FAIL / SKIP: $SKIP"
+          echo "${output}"
+
+          if [[ "$FAIL" -gt 0 ]]; then
+            echo "::warning ::${output}"
+          fi
+
+          jq -n \
+            --arg date "$(date --rfc-email)" \
+            --arg sha "$GITHUB_SHA" \
+            --arg total "$TOTAL" \
+            --arg pass "$PASS" \
+            --arg skip "$SKIP" \
+            --arg fail "$FAIL" \
+            --arg error "$ERROR" \
+            '{($date): { sha: $sha, total: $total, pass: $pass, skip: $skip, fail: $fail, error: $error }}' > '${{ steps.vars.outputs.TEST_SUMMARY_FILE }}'
+
+          HASH=$(sha1sum '${{ steps.vars.outputs.TEST_SUMMARY_FILE }}' | cut --delim=" " -f 1)
+          outputs HASH TOTAL PASS FAIL SKIP
+
+      - name: Upload SHA1/ID of 'test-summary'
+        uses: actions/upload-artifact@v7
+        with:
+          name: "${{ steps.summary.outputs.HASH }}"
+          path: "${{ steps.vars.outputs.TEST_SUMMARY_FILE }}"
+
+      - name: Upload test results summary
+        uses: actions/upload-artifact@v7
+        with:
+          name: test-summary
+          path: "${{ steps.vars.outputs.TEST_SUMMARY_FILE }}"
+
+      - name: Compare test failures VS reference
+        shell: bash
+        run: |
+          ## Compare test failures VS reference
+          REF_SUMMARY_FILE='reference/diffutils-gnu-full-result/test-results.json'
+          CURRENT_SUMMARY_FILE="results/test-results.json"
+
+          IGNORE_INTERMITTENT=".github/workflows/ignore-intermittent.txt"
+
+          # Build the comment in a directory of its own: 'reference/' holds the
+          # artifacts downloaded from the reference run, including its own
+          # 'comment' artifact, and re-uploading those would post a comparison
+          # belonging to another run (see https://github.com/uutils/diffutils/pull/262)
+          COMMENT_DIR="comment"
+          rm -rf ${COMMENT_DIR}
+          mkdir -p ${COMMENT_DIR}
+          echo ${{ github.event.number }} > ${COMMENT_DIR}/NR
+          COMMENT_LOG="${COMMENT_DIR}/result.txt"
+          : > "${COMMENT_LOG}"
+
+          COMPARISON_RESULT=0
+          if test -f "${CURRENT_SUMMARY_FILE}"; then
+            if test -s "${REF_SUMMARY_FILE}"; then
+              echo "Reference summary SHA1/ID: $(sha1sum -- "${REF_SUMMARY_FILE}")"
+              echo "Current summary SHA1/ID: $(sha1sum -- "${CURRENT_SUMMARY_FILE}")"
+
+              python3 util/compare_test_results.py \
+                --ignore-file "${IGNORE_INTERMITTENT}" \
+                --output "${COMMENT_LOG}" \
+                "${CURRENT_SUMMARY_FILE}" "${REF_SUMMARY_FILE}"
+
+              COMPARISON_RESULT=$?
+            else
+              echo "::warning ::Skipping test comparison; no usable reference summary is available at '${REF_SUMMARY_FILE}'."
+            fi
+          else
+            echo "::error ::Failed to find summary of test results (missing '${CURRENT_SUMMARY_FILE}'); failing early"
+            exit 1
+          fi
+
+          if [ ${COMPARISON_RESULT} -eq 1 ]; then
+            echo "::error ::Found new non-intermittent test failures"
+            exit 1
+          elif [ ${COMPARISON_RESULT} -ge 2 ]; then
+            # The comparison itself failed (e.g. an unusable reference summary).
+            # Don't post a comment rather than post a misleading one.
+            : > "${COMMENT_LOG}"
+            echo "::warning ::Could not compare the test results against the reference"
+          else
+            echo "::notice ::No new test failures detected"
+          fi
+
+      - name: Upload comparison log (for GnuComment workflow)
+        if: success() || failure()
+        uses: actions/upload-artifact@v7
+        with:
+          name: comment
+          path: comment/
+
+      - name: Report test results
+        if: success() || failure()
+        shell: bash
+        run: |
+          ## Report final results
+          echo "::notice ::GNU diffutils testsuite results:"
+          echo "::notice ::  Total tests: ${{ steps.summary.outputs.TOTAL }}"
+          echo "::notice ::  Passed: ${{ steps.summary.outputs.PASS }}"
+          echo "::notice ::  Failed: ${{ steps.summary.outputs.FAIL }}"
+          echo "::notice ::  Skipped: ${{ steps.summary.outputs.SKIP }}"
+
+          if [[ "${{ steps.summary.outputs.FAIL }}" -gt 0 ]]; then
+            PASS_RATE=$(( ${{ steps.summary.outputs.PASS }} * 100 / (${{ steps.summary.outputs.PASS }} + ${{ steps.summary.outputs.FAIL }}) ))
+            echo "::notice ::  Pass rate: ${PASS_RATE}%"
+          fi
@@ -0,0 +1,15 @@
+name: Security audit
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+jobs:
+  audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+      - uses: rustsec/audit-check@v2
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
@@ -0,0 +1,137 @@
+on: [push, pull_request]
+
+name: Basic CI
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: 0
+
+jobs:
+  check:
+    name: cargo check
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macOS-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v7
+      - run: cargo check
+
+  test:
+    name: cargo test
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macOS-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v7
+      - name: install GNU patch on MacOS
+        if: runner.os == 'macOS'
+        run: |
+          brew install gpatch
+      - name: set up PATH on Windows
+        # Needed to use GNU's patch.exe instead of Strawberry Perl patch
+        if: runner.os == 'Windows'
+        run: echo "C:\Program Files\Git\usr\bin" >> $env:GITHUB_PATH
+      - run: cargo test
+
+  fmt:
+    name: cargo fmt --all -- --check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - run: cargo fmt --all -- --check
+
+  clippy:
+    name: cargo clippy -- -D warnings
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macOS-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v7
+      - run: cargo clippy -- -D warnings
+
+  coverage:
+    name: Code Coverage
+    env:
+      RUSTC_BOOTSTRAP: 1
+    runs-on: ${{ matrix.job.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        job:
+          - { os: ubuntu-latest  , features: unix }
+          - { os: macos-latest   , features: macos }
+          - { os: windows-latest , features: windows }
+    steps:
+    - uses: actions/checkout@v7
+    - name: Initialize workflow variables
+      id: vars
+      shell: bash
+      run: |
+        ## VARs setup
+        outputs() { step_id="vars"; for var in "$@" ; do echo steps.${step_id}.outputs.${var}="${!var}"; echo "${var}=${!var}" >> $GITHUB_OUTPUT; done; }
+        # target-specific options
+        # * CODECOV_FLAGS
+        CODECOV_FLAGS=$( echo "${{ matrix.job.os }}" | sed 's/[^[:alnum:]]/_/g' )
+        outputs CODECOV_FLAGS
+
+    - name: install GNU patch on MacOS
+      if: runner.os == 'macOS'
+      run: |
+        brew install gpatch
+    - name: set up PATH on Windows
+      # Needed to use GNU's patch.exe instead of Strawberry Perl patch
+      if: runner.os == 'Windows'
+      run: echo "C:\Program Files\Git\usr\bin" >> $env:GITHUB_PATH
+    - name: Test
+      run: cargo test --all-features --no-fail-fast
+      env:
+        RUSTC_WRAPPER: ""
+        RUSTFLAGS: "-Cinstrument-coverage -Zcoverage-options=branch -Ccodegen-units=1 -Copt-level=0 -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
+        RUSTDOCFLAGS: "-Cpanic=abort"
+        LLVM_PROFILE_FILE: "diffutils-%p-%m.profraw"
+    - name: "`grcov` ~ install"
+      id: build_grcov
+      shell: bash
+      run: |
+        git clone --depth=1 https://github.com/mozilla/grcov.git ~/grcov/
+        cd ~/grcov
+        # Hardcode the version of crossbeam-epoch. See
+        # https://github.com/uutils/coreutils/issues/3680
+        sed -i -e "s|tempfile =|crossbeam-epoch = \"=0.9.8\"\ntempfile =|" Cargo.toml
+        cargo install --path .
+        cd -
+# Uncomment when the upstream issue
+# https://github.com/mozilla/grcov/issues/849 is fixed
+#      uses: actions-rs/install@v0.1
+#      with:
+#        crate: grcov
+#        version: latest
+#        use-tool-cache: false
+    - name: Generate coverage data (via `grcov`)
+      id: coverage
+      shell: bash
+      run: |
+        ## Generate coverage data
+        COVERAGE_REPORT_DIR="target/debug"
+        COVERAGE_REPORT_FILE="${COVERAGE_REPORT_DIR}/lcov.info"
+        mkdir -p "${COVERAGE_REPORT_DIR}"
+        # display coverage files
+        grcov . --output-type files --binary-path "${COVERAGE_REPORT_DIR}" | sort --unique
+        # generate coverage report
+        grcov . --output-type lcov --output-path "${COVERAGE_REPORT_FILE}" --binary-path "${COVERAGE_REPORT_DIR}" --branch
+        echo "report=${COVERAGE_REPORT_FILE}" >> $GITHUB_OUTPUT
+    - name: Upload coverage results (to Codecov.io)
+      uses: codecov/codecov-action@v7
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}
+        files: ${{ steps.coverage.outputs.report }}
+        ## flags: IntegrationTests, UnitTests, ${{ steps.vars.outputs.CODECOV_FLAGS }}
+        flags: ${{ steps.vars.outputs.CODECOV_FLAGS }}
+        name: codecov-umbrella
+        fail_ci_if_error: false
@@ -0,0 +1,37 @@
+name: CodSpeed
+
+on:
+  push:
+    branches:
+      - "main"
+  pull_request:
+  # `workflow_dispatch` allows CodSpeed to trigger backtest
+  # performance analysis in order to generate initial data.
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  codspeed:
+    name: Run benchmarks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Setup rust toolchain, cache and cargo-codspeed binary
+        uses: moonrepo/setup-rust@v1
+        with:
+          channel: stable
+          cache-target: release
+          bins: cargo-codspeed
+
+      - name: Build the benchmark target(s)
+        run: cargo codspeed build -m simulation
+
+      - name: Run the benchmarks
+        uses: CodSpeedHQ/action@v5
+        with:
+          mode: simulation
+          run: cargo codspeed run
@@ -0,0 +1,82 @@
+name: Fuzzing
+
+# spell-checker:ignore fuzzer
+
+env:
+  CARGO_INCREMENTAL: 0
+  RUSTC_BOOTSTRAP: 1
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
+jobs:
+  fuzz-build:
+    name: Build the fuzzers
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - name: Install `cargo-fuzz`
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-fuzz
+      - uses: Swatinem/rust-cache@v2
+        with:
+          shared-key: "cargo-fuzz-cache-key"
+          cache-directories: "fuzz/target"
+      - name: Run `cargo-fuzz build`
+        # https://github.com/rust-fuzz/cargo-fuzz/issues/398
+        run: cargo fuzz build --target host-tuple
+
+  fuzz-run:
+    needs: fuzz-build
+    name: Run the fuzzers
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    env:
+      RUN_FOR: 60
+    strategy:
+      matrix:
+        test-target:
+          - { name: fuzz_cmp, should_pass: true }
+          - { name: fuzz_cmp_args, should_pass: true }
+          - { name: fuzz_ed, should_pass: true }
+          - { name: fuzz_normal, should_pass: true }
+          - { name: fuzz_patch, should_pass: true }
+          - { name: fuzz_side, should_pass: true }
+    steps:
+      - uses: actions/checkout@v7
+      - name: Install `cargo-fuzz`
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-fuzz
+      - uses: Swatinem/rust-cache@v2
+        with:
+          shared-key: "cargo-fuzz-cache-key"
+          cache-directories: "fuzz/target"
+      - name: Restore Cached Corpus
+        uses: actions/cache/restore@v6
+        with:
+          key: corpus-cache-${{ matrix.test-target.name }}
+          path: |
+            fuzz/corpus/${{ matrix.test-target.name }}
+      - name: Run ${{ matrix.test-target.name }} for XX seconds
+        shell: bash
+        continue-on-error: ${{ !matrix.test-target.should_pass }}
+        run: |
+          cargo fuzz run --target host-tuple ${{ matrix.test-target.name }} -- -max_total_time=${{ env.RUN_FOR }} -detect_leaks=0
+      - name: Save Corpus Cache
+        uses: actions/cache/save@v6
+        with:
+          key: corpus-cache-${{ matrix.test-target.name }}
+          path: |
+            fuzz/corpus/${{ matrix.test-target.name }}
@@ -0,0 +1,296 @@
+# This file was autogenerated by dist: https://axodotdev.github.io/cargo-dist
+#
+# Copyright 2022-2024, axodotdev
+# SPDX-License-Identifier: MIT or Apache-2.0
+#
+# CI that:
+#
+# * checks for a Git Tag that looks like a release
+# * builds artifacts with dist (archives, installers, hashes)
+# * uploads those artifacts to temporary workflow zip
+# * on success, uploads the artifacts to a GitHub Release
+#
+# Note that the GitHub Release will be created with a generated
+# title/body based on your changelogs.
+
+name: Release
+permissions:
+  "contents": "write"
+
+# This task will run whenever you push a git tag that looks like a version
+# like "1.0.0", "v0.1.0-prerelease.1", "my-app/0.1.0", "releases/v1.0.0", etc.
+# Various formats will be parsed into a VERSION and an optional PACKAGE_NAME, where
+# PACKAGE_NAME must be the name of a Cargo package in your workspace, and VERSION
+# must be a Cargo-style SemVer Version (must have at least major.minor.patch).
+#
+# If PACKAGE_NAME is specified, then the announcement will be for that
+# package (erroring out if it doesn't have the given version or isn't dist-able).
+#
+# If PACKAGE_NAME isn't specified, then the announcement will be for all
+# (dist-able) packages in the workspace with that version (this mode is
+# intended for workspaces with only one dist-able package, or with all dist-able
+# packages versioned/released in lockstep).
+#
+# If you push multiple tags at once, separate instances of this workflow will
+# spin up, creating an independent announcement for each one. However, GitHub
+# will hard limit this to 3 tags per commit, as it will assume more tags is a
+# mistake.
+#
+# If there's a prerelease-style suffix to the version, then the release(s)
+# will be marked as a prerelease.
+on:
+  pull_request:
+  push:
+    tags:
+      - '**[0-9]+.[0-9]+.[0-9]+*'
+
+jobs:
+  # Run 'dist plan' (or host) to determine what tasks we need to do
+  plan:
+    runs-on: "ubuntu-22.04"
+    outputs:
+      val: ${{ steps.plan.outputs.manifest }}
+      tag: ${{ !github.event.pull_request && github.ref_name || '' }}
+      tag-flag: ${{ !github.event.pull_request && format('--tag={0}', github.ref_name) || '' }}
+      publishing: ${{ !github.event.pull_request }}
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          submodules: recursive
+      - name: Install dist
+        # we specify bash to get pipefail; it guards against the `curl` command
+        # failing. otherwise `sh` won't catch that `curl` returned non-0
+        shell: bash
+        run: "curl --proto '=https' --tlsv1.2 -LsSf https://github.com/axodotdev/cargo-dist/releases/download/v0.33.0/cargo-dist-installer.sh | sh"
+      - name: Cache dist
+        uses: actions/upload-artifact@v7
+        with:
+          name: cargo-dist-cache
+          path: ~/.cargo/bin/dist
+      # sure would be cool if github gave us proper conditionals...
+      # so here's a doubly-nested ternary-via-truthiness to try to provide the best possible
+      # functionality based on whether this is a pull_request, and whether it's from a fork.
+      # (PRs run on the *source* but secrets are usually on the *target* -- that's *good*
+      # but also really annoying to build CI around when it needs secrets to work right.)
+      - id: plan
+        run: |
+          dist ${{ (!github.event.pull_request && format('host --steps=create --tag={0}', github.ref_name)) || 'plan' }} --output-format=json > plan-dist-manifest.json
+          echo "dist ran successfully"
+          cat plan-dist-manifest.json
+          echo "manifest=$(jq -c "." plan-dist-manifest.json)" >> "$GITHUB_OUTPUT"
+      - name: "Upload dist-manifest.json"
+        uses: actions/upload-artifact@v7
+        with:
+          name: artifacts-plan-dist-manifest
+          path: plan-dist-manifest.json
+
+  # Build and packages all the platform-specific things
+  build-local-artifacts:
+    name: build-local-artifacts (${{ join(matrix.targets, ', ') }})
+    # Let the initial task tell us to not run (currently very blunt)
+    needs:
+      - plan
+    if: ${{ fromJson(needs.plan.outputs.val).ci.github.artifacts_matrix.include != null && (needs.plan.outputs.publishing == 'true' || fromJson(needs.plan.outputs.val).ci.github.pr_run_mode == 'upload') }}
+    strategy:
+      fail-fast: false
+      # Target platforms/runners are computed by dist in create-release.
+      # Each member of the matrix has the following arguments:
+      #
+      # - runner: the github runner
+      # - dist-args: cli flags to pass to dist
+      # - install-dist: expression to run to install dist on the runner
+      #
+      # Typically there will be:
+      # - 1 "global" task that builds universal installers
+      # - N "local" tasks that build each platform's binaries and platform-specific installers
+      matrix: ${{ fromJson(needs.plan.outputs.val).ci.github.artifacts_matrix }}
+    runs-on: ${{ matrix.runner }}
+    container: ${{ matrix.container && matrix.container.image || null }}
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      BUILD_MANIFEST_NAME: target/distrib/${{ join(matrix.targets, '-') }}-dist-manifest.json
+    steps:
+      - name: enable windows longpaths
+        run: |
+          git config --global core.longpaths true
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          submodules: recursive
+      - name: Install Rust non-interactively if not already installed
+        if: ${{ matrix.container }}
+        run: |
+          if ! command -v cargo > /dev/null 2>&1; then
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+            echo "$HOME/.cargo/bin" >> $GITHUB_PATH
+          fi
+      - name: Install dist
+        run: ${{ matrix.install_dist.run }}
+      # Get the dist-manifest
+      - name: Fetch local artifacts
+        uses: actions/download-artifact@v8
+        with:
+          pattern: artifacts-*
+          path: target/distrib/
+          merge-multiple: true
+      - name: Install dependencies
+        run: |
+          ${{ matrix.packages_install }}
+      - name: Build artifacts
+        run: |
+          # Actually do builds and make zips and whatnot
+          dist build ${{ needs.plan.outputs.tag-flag }} --print=linkage --output-format=json ${{ matrix.dist_args }} > dist-manifest.json
+          echo "dist ran successfully"
+      - id: cargo-dist
+        name: Post-build
+        # We force bash here just because github makes it really hard to get values up
+        # to "real" actions without writing to env-vars, and writing to env-vars has
+        # inconsistent syntax between shell and powershell.
+        shell: bash
+        run: |
+          # Parse out what we just built and upload it to scratch storage
+          echo "paths<<EOF" >> "$GITHUB_OUTPUT"
+          dist print-upload-files-from-manifest --manifest dist-manifest.json >> "$GITHUB_OUTPUT"
+          echo "EOF" >> "$GITHUB_OUTPUT"
+
+          cp dist-manifest.json "$BUILD_MANIFEST_NAME"
+      - name: "Upload artifacts"
+        uses: actions/upload-artifact@v7
+        with:
+          name: artifacts-build-local-${{ join(matrix.targets, '_') }}
+          path: |
+            ${{ steps.cargo-dist.outputs.paths }}
+            ${{ env.BUILD_MANIFEST_NAME }}
+
+  # Build and package all the platform-agnostic(ish) things
+  build-global-artifacts:
+    needs:
+      - plan
+      - build-local-artifacts
+    runs-on: "ubuntu-22.04"
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      BUILD_MANIFEST_NAME: target/distrib/global-dist-manifest.json
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          submodules: recursive
+      - name: Install cached dist
+        uses: actions/download-artifact@v8
+        with:
+          name: cargo-dist-cache
+          path: ~/.cargo/bin/
+      - run: chmod +x ~/.cargo/bin/dist
+      # Get all the local artifacts for the global tasks to use (for e.g. checksums)
+      - name: Fetch local artifacts
+        uses: actions/download-artifact@v8
+        with:
+          pattern: artifacts-*
+          path: target/distrib/
+          merge-multiple: true
+      - id: cargo-dist
+        shell: bash
+        run: |
+          dist build ${{ needs.plan.outputs.tag-flag }} --output-format=json "--artifacts=global" > dist-manifest.json
+          echo "dist ran successfully"
+
+          # Parse out what we just built and upload it to scratch storage
+          echo "paths<<EOF" >> "$GITHUB_OUTPUT"
+          jq --raw-output ".upload_files[]" dist-manifest.json >> "$GITHUB_OUTPUT"
+          echo "EOF" >> "$GITHUB_OUTPUT"
+
+          cp dist-manifest.json "$BUILD_MANIFEST_NAME"
+      - name: "Upload artifacts"
+        uses: actions/upload-artifact@v7
+        with:
+          name: artifacts-build-global
+          path: |
+            ${{ steps.cargo-dist.outputs.paths }}
+            ${{ env.BUILD_MANIFEST_NAME }}
+  # Determines if we should publish/announce
+  host:
+    needs:
+      - plan
+      - build-local-artifacts
+      - build-global-artifacts
+    # Only run if we're "publishing", and only if plan, local and global didn't fail (skipped is fine)
+    if: ${{ always() && needs.plan.result == 'success' && needs.plan.outputs.publishing == 'true' && (needs.build-global-artifacts.result == 'skipped' || needs.build-global-artifacts.result == 'success') && (needs.build-local-artifacts.result == 'skipped' || needs.build-local-artifacts.result == 'success') }}
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    runs-on: "ubuntu-22.04"
+    outputs:
+      val: ${{ steps.host.outputs.manifest }}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          submodules: recursive
+      - name: Install cached dist
+        uses: actions/download-artifact@v8
+        with:
+          name: cargo-dist-cache
+          path: ~/.cargo/bin/
+      - run: chmod +x ~/.cargo/bin/dist
+      # Fetch artifacts from scratch-storage
+      - name: Fetch artifacts
+        uses: actions/download-artifact@v8
+        with:
+          pattern: artifacts-*
+          path: target/distrib/
+          merge-multiple: true
+      - id: host
+        shell: bash
+        run: |
+          dist host ${{ needs.plan.outputs.tag-flag }} --steps=upload --steps=release --output-format=json > dist-manifest.json
+          echo "artifacts uploaded and released successfully"
+          cat dist-manifest.json
+          echo "manifest=$(jq -c "." dist-manifest.json)" >> "$GITHUB_OUTPUT"
+      - name: "Upload dist-manifest.json"
+        uses: actions/upload-artifact@v7
+        with:
+          # Overwrite the previous copy
+          name: artifacts-dist-manifest
+          path: dist-manifest.json
+      # Create a GitHub Release while uploading all files to it
+      - name: "Download GitHub Artifacts"
+        uses: actions/download-artifact@v8
+        with:
+          pattern: artifacts-*
+          path: artifacts
+          merge-multiple: true
+      - name: Cleanup
+        run: |
+          # Remove the granular manifests
+          rm -f artifacts/*-dist-manifest.json
+      - name: Create GitHub Release
+        env:
+          PRERELEASE_FLAG: "${{ fromJson(steps.host.outputs.manifest).announcement_is_prerelease && '--prerelease' || '' }}"
+          ANNOUNCEMENT_TITLE: "${{ fromJson(steps.host.outputs.manifest).announcement_title }}"
+          ANNOUNCEMENT_BODY: "${{ fromJson(steps.host.outputs.manifest).announcement_github_body }}"
+          RELEASE_COMMIT: "${{ github.sha }}"
+        run: |
+          # Write and read notes from a file to avoid quoting breaking things
+          echo "$ANNOUNCEMENT_BODY" > $RUNNER_TEMP/notes.txt
+
+          gh release create "${{ needs.plan.outputs.tag }}" --target "$RELEASE_COMMIT" $PRERELEASE_FLAG --title "$ANNOUNCEMENT_TITLE" --notes-file "$RUNNER_TEMP/notes.txt" artifacts/*
+
+  announce:
+    needs:
+      - plan
+      - host
+    # use "always() && ..." to allow us to wait for all publish jobs while
+    # still allowing individual publish jobs to skip themselves (for prereleases).
+    # "host" however must run to completion, no skipping allowed!
+    if: ${{ always() && needs.host.result == 'success' }}
+    runs-on: "ubuntu-22.04"
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          submodules: recursive
@@ -0,0 +1,28 @@
+# spell-checker:ignore wasip
+name: WASI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+# End the current execution if there is a new changeset in the PR.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
+jobs:
+  test_wasi:
+    name: Tests
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v7
+    - uses: dtolnay/rust-toolchain@stable
+      with:
+        targets: wasm32-wasip1
+    - name: check
+      run: cargo check --target wasm32-wasip1
@@ -0,0 +1,3 @@
+/target
+*.swp
+/tests/test-results.json
@@ -0,0 +1,48 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+exclude: ^tests/fixtures/
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: check-added-large-files
+      - id: check-executables-have-shebangs
+      - id: check-json
+        exclude: '\.vscode/(cSpell|extensions)\.json' # cSpell.json and extensions.json use comments
+      - id: check-shebang-scripts-are-executable
+        exclude: '.+\.rs' # would be triggered by #![some_attribute]
+      - id: check-symlinks
+      - id: check-toml
+      - id: check-yaml
+        args: [ --allow-multiple-documents ]
+      - id: destroyed-symlinks
+      - id: end-of-file-fixer
+      - id: mixed-line-ending
+        args: [ --fix=lf ]
+      - id: trailing-whitespace
+
+  - repo: local
+    hooks:
+      - id: rust-linting
+        name: Rust linting
+        description: Run cargo fmt on files included in the commit.
+        entry: cargo +stable fmt --
+        pass_filenames: true
+        types: [file, rust]
+        language: system
+      - id: rust-clippy
+        name: Rust clippy
+        description: Run cargo clippy on files included in the commit.
+        entry: cargo +stable clippy --workspace --all-targets --all-features -- -D warnings
+        pass_filenames: false
+        types: [file, rust]
+        language: system
+      - id: cspell
+        name: Code spell checker (cspell)
+        description: Run cspell to check for spelling errors (if available).
+        entry: bash -c 'if command -v cspell >/dev/null 2>&1; then cspell --no-must-find-files -- "$@"; else echo "cspell not found, skipping spell check"; exit 0; fi' --
+        pass_filenames: true
+        language: system
+
+ci:
+  skip: [rust-linting, rust-clippy, cspell]
@@ -0,0 +1,32 @@
+# Contributing to diffutils
+
+Hi! Welcome to uutils/diffutils, and thanks for wanting to contribute!
+
+This project follows the shared conventions of the [uutils](https://github.com/uutils)
+organization. Before opening a pull request, please read:
+
+- Our **[Review Guidelines](https://uutils.github.io/reviews/)** — what we expect
+  from a pull request and how reviews are carried out.
+- Our community's [CODE_OF_CONDUCT.md](./CODE_OF_CONDUCT.md), if present.
+
+Finally, feel free to join our [Discord](https://discord.gg/wQVJbvJ)!
+
+> [!WARNING]
+> uutils is original code and cannot contain any code from GNU or other
+> strongly-licensed (GPL/LGPL) implementations. We **cannot** accept changes
+> based on the GNU source code, and you **must not link** to it either. You may
+> look at permissively-licensed implementations (MIT/BSD) and read the GNU
+> *manuals* — never the GNU *source*.
+
+## In short
+
+- Discuss non-trivial changes in an issue **before** writing the code.
+- Keep pull requests **small, self-contained, and descriptively titled**
+  (e.g. `diffutils: fix ...`).
+- Make sure CI passes: tests are green, `rustfmt` is satisfied, and there are
+  no `clippy` warnings.
+- Add tests for new behavior; don't let coverage regress.
+- Write small, atomic commits annotated with the component you touched.
+
+See the [Review Guidelines](https://uutils.github.io/reviews/) for the full
+details.
@@ -0,0 +1,8 @@
+Copyright (c) Michael Howell
+Copyright (c) uutils developers
+
+Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+option. All files in the project carrying such notice may not be
+copied, modified, or distributed except according to those terms.
@@ -0,0 +1,917 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "aho-corasick"
+version = "1.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ddd31a130427c27518df266943a5308ed92d4b226cc639f5a8f1002816174301"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "android_system_properties"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "819e7219dbd41043ac279b19830f2efc897156490d7fd6ea916720117ee66311"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "anstyle"
+version = "1.0.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "940b3a0ca603d1eade50a4846a2afffd5ef57a9feac2c0e2ec2e14f9ead76000"
+
+[[package]]
+name = "anyhow"
+version = "1.0.104"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "330a5ed07fa54e4702c9d6c4174f74427fc0ef6e214bbd677ae50a5099946470"
+
+[[package]]
+name = "approx"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cab112f0a86d568ea0e627cc1d6be74a1e9cd55214684db5561995f6dad897c6"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "assert_cmd"
+version = "2.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2aa3a22042e45de04255c7bf3626e239f450200fd0493c1e382263544b20aea6"
+dependencies = [
+ "anstyle",
+ "bstr",
+ "libc",
+ "predicates",
+ "predicates-core",
+ "predicates-tree",
+ "wait-timeout",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
+
+[[package]]
+name = "bitflags"
+version = "2.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "843867be96c8daad0d758b57df9392b6d8d271134fce549de6ce169ff98a92af"
+
+[[package]]
+name = "bstr"
+version = "1.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "63044e1ae8e69f3b5a92c736ca6269b8d12fa7efe39bf34ddb06d102cf0e2cab"
+dependencies = [
+ "memchr",
+ "regex-automata",
+ "serde",
+]
+
+[[package]]
+name = "bumpalo"
+version = "3.20.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d20789868f4b01b2f2caec9f5c4e0213b41e3e5702a50157d699ae31ced2fcb"
+
+[[package]]
+name = "cc"
+version = "1.2.60"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43c5703da9466b66a946814e1adf53ea2c90f10063b86290cc9eb67ce3478a20"
+dependencies = [
+ "find-msvc-tools",
+ "shlex",
+]
+
+[[package]]
+name = "cfg-if"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
+
+[[package]]
+name = "cfg_aliases"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
+
+[[package]]
+name = "chacha20"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f8d983286843e49675a4b7a2d174efe136dc93a18d69130dd18198a6c167601"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "rand_core",
+]
+
+[[package]]
+name = "chrono"
+version = "0.4.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1aa79e62e7697b8e29b513a68abacf485adcd1fe8284a4316c5ae868e6633327"
+dependencies = [
+ "iana-time-zone",
+ "js-sys",
+ "num-traits",
+ "wasm-bindgen",
+ "windows-link",
+]
+
+[[package]]
+name = "clap"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b193af5b67834b676abd72466a96c1024e6a6ad978a1f484bd90b85c94041351"
+dependencies = [
+ "clap_builder",
+]
+
+[[package]]
+name = "clap_builder"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "714a53001bf66416adb0e2ef5ac857140e7dc3a0c48fb28b2f10762fc4b5069f"
+dependencies = [
+ "anstyle",
+ "clap_lex",
+ "terminal_size",
+]
+
+[[package]]
+name = "clap_lex"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9"
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+[[package]]
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+dependencies = [
+ "anyhow",
+ "cc",
+ "colored",
+ "getrandom",
+ "glob",
+ "nix",
+ "serde",
+ "serde_json",
+ "statrs",
+]
+
+[[package]]
+name = "codspeed-divan-compat"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc7e48c4e555e60b894144b14df1e893a7317b9f4000b1492ace3041479b12cc"
+dependencies = [
+ "clap",
+ "codspeed",
+ "codspeed-divan-compat-macros",
+ "codspeed-divan-compat-walltime",
+ "regex",
+]
+
+[[package]]
+name = "codspeed-divan-compat-macros"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1eb62a7a8d4cc6b79b18dcbac670b3202f4c8c901ca8ea701ab42190f0b14799"
+dependencies = [
+ "divan-macros",
+ "itertools",
+ "proc-macro-crate",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "codspeed-divan-compat-walltime"
+version = "6.0.0"
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+ "windows-interface",
+ "windows-link",
+ "windows-result",
+ "windows-strings",
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+ "syn",
+]
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+name = "windows-interface"
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+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
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+name = "windows-link"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+name = "windows-strings"
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+dependencies = [
+ "windows-link",
+]
+
+[[package]]
+name = "windows-sys"
+version = "0.61.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
+dependencies = [
+ "windows-link",
+]
+
+[[package]]
+name = "winnow"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09dac053f1cd375980747450bfc7250c264eaae0583872e845c0c7cd578872b5"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "yansi"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe53a6657fd280eaa890a3bc59152892ffa3e30101319d168b781ed6529b049"
+
+[[package]]
+name = "zmij"
+version = "1.0.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8848ee67ecc8aedbaf3e4122217aff892639231befc6a1b58d29fff4c2cabaa"
@@ -0,0 +1,91 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "diffutils"
+version = "0.6.0"
+build = false
+autolib = false
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "A CLI app for generating diff files"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/uutils/diffutils"
+
+[features]
+feat_bench_not_cmp = []
+feat_bench_not_diff = []
+
+[lib]
+name = "diffutilslib"
+path = "src/lib.rs"
+
+[[bin]]
+name = "diffutils"
+path = "src/main.rs"
+
+[[test]]
+name = "integration"
+path = "tests/integration.rs"
+
+[[bench]]
+name = "bench_diffutils"
+path = "benches/bench-diffutils.rs"
+harness = false
+
+[dependencies.chrono]
+version = "0.4.38"
+
+[dependencies.diff]
+version = "0.1.13"
+
+[dependencies.itoa]
+version = "1.0.11"
+
+[dependencies.regex]
+version = "1.10.4"
+
+[dependencies.same-file]
+version = "1.0.6"
+
+[dependencies.unicode-width]
+version = "0.2.0"
+
+[dev-dependencies.assert_cmd]
+version = "2.0.14"
+
+[dev-dependencies.divan]
+version = "6.0.0"
+package = "codspeed-divan-compat"
+
+[dev-dependencies.predicates]
+version = "3.1.0"
+
+[dev-dependencies.pretty_assertions]
+version = "1.4.0"
+
+[dev-dependencies.rand]
+version = "0.10.0"
+
+[dev-dependencies.tempfile]
+version = "3.26.0"
+
+[profile.dist]
+inherits = "release"
+
+[profile.release]
+lto = "thin"
+codegen-units = 1
+panic = "abort"
@@ -0,0 +1,52 @@
+[package]
+name = "diffutils"
+version = "0.6.0"
+edition = "2021"
+description = "A CLI app for generating diff files"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/uutils/diffutils"
+
+[lib]
+name = "diffutilslib"
+path = "src/lib.rs"
+
+[[bin]]
+name = "diffutils"
+path = "src/main.rs"
+
+[dependencies]
+chrono = "0.4.38"
+diff = "0.1.13"
+itoa = "1.0.11"
+regex = "1.10.4"
+same-file = "1.0.6"
+unicode-width = "0.2.0"
+
+[dev-dependencies]
+assert_cmd = "2.0.14"
+divan = { version = "6.0.0", package = "codspeed-divan-compat" }
+pretty_assertions = "1.4.0"
+predicates = "3.1.0"
+rand = "0.10.0"
+tempfile = "3.26.0"
+
+[profile.release]
+lto = "thin"
+codegen-units = 1
+panic = "abort"
+
+# alias profile for 'dist'
+[profile.dist]
+inherits = "release"
+
+[[bench]]
+name = "bench_diffutils"
+path = "benches/bench-diffutils.rs"
+harness = false
+
+[features]
+# default = ["feat_bench_not_diff"]
+# Turn bench for diffutils cmp off
+feat_bench_not_cmp = []
+# Turn bench for diffutils diff off
+feat_bench_not_diff = []
@@ -0,0 +1,176 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
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+   for use, reproduction, or distribution of Your modifications, or
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+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
+   risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
+   or other liability obligations and/or rights consistent with this
+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
@@ -0,0 +1,14 @@
+# Recursive directory comparison
+
+Source: crates.io `diffutils` 0.6.0, https://github.com/uutils/diffutils.
+The vendor copy retains the upstream licenses.
+
+The public library exposes comparison functions but not the diff CLI entry point.
+The vendor copy retains that CLI parser and dispatcher.
+
+- `src/params.rs` accepts `-r` and `--recursive`.
+- `src/diff.rs` recursively compares directory entries in lexical order.
+- The recursive path reuses the upstream file comparison implementation.
+- `tools.txt` exposes the component as `diff` and `cmp`.
+
+`search-test.nu` compares identical directories and changed nested files against GNU diff.
@@ -0,0 +1,61 @@
+[![Crates.io](https://img.shields.io/crates/v/diffutils.svg)](https://crates.io/crates/diffutils)
+[![Discord](https://img.shields.io/badge/discord-join-7289DA.svg?logo=discord&longCache=true&style=flat)](https://discord.gg/wQVJbvJ)
+[![License](http://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/uutils/diffutils/blob/main/LICENSE)
+[![dependency status](https://deps.rs/repo/github/uutils/diffutils/status.svg)](https://deps.rs/repo/github/uutils/diffutils)
+[![CodSpeed](https://img.shields.io/endpoint?url=https://codspeed.io/badge.json)](https://codspeed.io/uutils/diffutils?utm_source=badge)
+
+[![CodeCov](https://codecov.io/gh/uutils/diffutils/branch/main/graph/badge.svg)](https://codecov.io/gh/uutils/diffutils)
+
+The goal of this package is to be a drop-in replacement for the [diffutils commands](https://www.gnu.org/software/diffutils/) (diff, cmp, diff3, sdiff) in Rust.
+
+Based on the incomplete diff generator in https://github.com/rust-lang/rust/blob/master/src/tools/compiletest/src/runtest.rs, and made to be compatible with GNU's diff and patch tools.
+
+
+## Installation
+
+Ensure you have Rust installed on your system. You can install Rust through [rustup](https://rustup.rs/).
+
+Clone the repository and build the project using Cargo:
+
+```bash
+git clone https://github.com/uutils/diffutils.git
+cd diffutils
+cargo build --release
+```
+
+## Example
+
+```bash
+
+cat <<EOF >fruits_old.txt
+Apple
+Banana
+Cherry
+EOF
+
+cat <<EOF >fruits_new.txt
+Apple
+Fig
+Cherry
+EOF
+
+$ cargo run -- diff -u fruits_old.txt fruits_new.txt
+    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
+     Running `target/debug/diffutils -u fruits_old.txt fruits_new.txt`
+--- fruits_old.txt
+++ fruits_new.txt
+@@ -1,3 +1,3 @@
+ Apple
+-Banana
+Fig
+ Cherry
+
+```
+
+## License
+
+This project is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
@@ -0,0 +1,44 @@
+# Security Policy
+
+## Supported Versions
+
+We provide security updates only for the latest released version of `uutils/diffutils`.
+Older versions may not receive patches.
+If you are using a version packaged by your Linux distribution, please check with your distribution maintainers for their update policy.
+
+---
+
+## Reporting a Vulnerability
+
+**Do not open public GitHub issues for security vulnerabilities.**
+This prevents accidental disclosure before a fix is available.
+
+Instead, please use the following method:
+
+- **Email:** [sylvestre@debian.org](mailto:Sylvestre@debian.org)
+- **Encryption (optional):** You may encrypt your report using our PGP key:
+Fingerprint: B60D B599 4D39 BEC4 D1A9 5CCF 7E65 28DA 752F 1BE1
+---
+
+### What to Include in Your Report
+
+To help us investigate and resolve the issue quickly, please include as much detail as possible:
+
+- **Type of issue:** e.g. privilege escalation, information disclosure.
+- **Location in the source:** file path, commit hash, branch, or tag.
+- **Steps to reproduce:** exact commands, test cases, or scripts.
+- **Special configuration:** any flags, environment variables, or system setup required.
+- **Affected systems:** OS/distribution and version(s) where the issue occurs.
+- **Impact:** your assessment of the potential severity (DoS, RCE, data leak, etc.).
+
+---
+
+## Disclosure Policy
+
+We follow a **Coordinated Vulnerability Disclosure (CVD)** process:
+
+1. We will acknowledge receipt of your report within **10 days**.
+2. We will investigate, reproduce, and assess the issue.
+3. We will provide a timeline for developing and releasing a fix.
+4. Once a fix is available, we will publish a GitHub Security Advisory.
+5. You will be credited in the advisory unless you request anonymity.
@@ -0,0 +1,377 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+//! Benches for all utils in diffutils.
+//!
+//! There is a file generator included to create files of different sizes for comparison. \
+//! Set the TEMP_DIR const to keep the files. df_to_ files have small changes in them, search for '#'. \
+//! File generation up to 1 GB is really fast, Benchmarking above 100 MB takes very long.
+
+/// Generate test files with these sizes in KB.
+const FILE_SIZE_KILO_BYTES: [u64; 4] = [100, 1 * MB, 10 * MB, 25 * MB];
+// const FILE_SIZE_KILO_BYTES: [u64; 3] = [100, 1 * MB, 5 * MB];
+// Empty String to use TempDir (files will be removed after test) or specify dir to keep generated files
+const TEMP_DIR: &str = "";
+const NUM_DIFF: u64 = 4;
+// just for FILE_SIZE_KILO_BYTES
+const MB: u64 = 1_000;
+const CHANGE_CHAR: u8 = b'#';
+
+#[cfg(not(feature = "feat_bench_not_cmp"))]
+mod diffutils_cmp {
+    use std::hint::black_box;
+
+    use diffutilslib::cmp;
+    use divan::Bencher;
+
+    use crate::{binary, prepare::*, FILE_SIZE_KILO_BYTES};
+
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmp_compare_files_equal(bencher: Bencher, kb: u64) {
+        let (from, to) = get_context().get_test_files_equal(kb);
+        let cmd = format!("cmp {from} {to}");
+        let opts = str_to_options(&cmd).into_iter().peekable();
+        let params = cmp::parse_params(opts).unwrap();
+
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| params.clone())
+            .bench_refs(|params| black_box(cmp::cmp(&params).unwrap()));
+    }
+
+    // bench the actual compare; cmp exits on first difference
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmp_compare_files_different(bencher: Bencher, bytes: u64) {
+        let (from, to) = get_context().get_test_files_different(bytes);
+        let cmd = format!("cmp {from} {to} -s");
+        let opts = str_to_options(&cmd).into_iter().peekable();
+        let params = cmp::parse_params(opts).unwrap();
+
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| params.clone())
+            .bench_refs(|params| black_box(cmp::cmp(&params).unwrap()));
+    }
+
+    // bench original GNU cmp
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmd_cmp_gnu_equal(bencher: Bencher, bytes: u64) {
+        let (from, to) = get_context().get_test_files_equal(bytes);
+        let args_str = format!("{from} {to}");
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| args_str.clone())
+            .bench_refs(|cmd_args| binary::bench_binary("cmp", cmd_args));
+    }
+
+    // bench the compiled release version
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmd_cmp_release_equal(bencher: Bencher, bytes: u64) {
+        let (from, to) = get_context().get_test_files_equal(bytes);
+        let args_str = format!("cmp {from} {to}");
+
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| args_str.clone())
+            .bench_refs(|cmd_args| binary::bench_binary("target/release/diffutils", cmd_args));
+    }
+}
+
+#[cfg(not(feature = "feat_bench_not_diff"))]
+mod diffutils_diff {
+    // use std::hint::black_box;
+
+    use crate::{binary, prepare::*, FILE_SIZE_KILO_BYTES};
+    // use diffutilslib::params;
+    use divan::Bencher;
+
+    // bench the actual compare
+    // TODO diff does not have a diff function
+    //     #[divan::bench(args = [100_000,10_000])]
+    //     fn diff_compare_files(bencher: Bencher, bytes: u64) {
+    //         let (from, to) = gen_testfiles(lines, 0, "id");
+    //         let cmd = format!("cmp {from} {to}");
+    //         let opts = str_to_options(&cmd).into_iter().peekable();
+    //         let params = params::parse_params(opts).unwrap();
+    //
+    //         bencher
+    //             // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+    //             .with_inputs(|| params.clone())
+    //             .bench_refs(|params| diff::diff(&params).unwrap());
+    //     }
+
+    // bench original GNU diff
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmd_diff_gnu_equal(bencher: Bencher, bytes: u64) {
+        let (from, to) = get_context().get_test_files_equal(bytes);
+        let args_str = format!("{from} {to}");
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| args_str.clone())
+            .bench_refs(|cmd_args| binary::bench_binary("diff", cmd_args));
+    }
+
+    // bench the compiled release version
+    #[divan::bench(args = FILE_SIZE_KILO_BYTES)]
+    fn cmd_diff_release_equal(bencher: Bencher, bytes: u64) {
+        let (from, to) = get_context().get_test_files_equal(bytes);
+        let args_str = format!("diff {from} {to}");
+
+        bencher
+            // .with_inputs(|| prepare::cmp_params_identical_testfiles(lines))
+            .with_inputs(|| args_str.clone())
+            .bench_refs(|cmd_args| binary::bench_binary("target/release/diffutils", cmd_args));
+    }
+}
+
+mod parser {
+    use std::hint::black_box;
+
+    use diffutilslib::{cmp, params};
+    use divan::Bencher;
+
+    use crate::prepare::str_to_options;
+
+    // bench the time it takes to parse the command line arguments
+    #[divan::bench]
+    fn cmp_parser(bencher: Bencher) {
+        let cmd = "cmd file_1.txt file_2.txt -bl n10M --ignore-initial=100KiB:1MiB";
+        let args = str_to_options(&cmd).into_iter().peekable();
+        bencher
+            .with_inputs(|| args.clone())
+            .bench_values(|data| black_box(cmp::parse_params(data)));
+    }
+
+    // // test the impact on the benchmark if not converting the cmd to Vec<OsString> (doubles for parse)
+    // #[divan::bench]
+    // fn cmp_parser_no_prepare() {
+    //     let cmd = "cmd file_1.txt file_2.txt -bl n10M --ignore-initial=100KiB:1MiB";
+    //     let args = str_to_options(&cmd).into_iter().peekable();
+    //     let _ = cmp::parse_params(args);
+    // }
+
+    // bench the time it takes to parse the command line arguments
+    #[divan::bench]
+    fn diff_parser(bencher: Bencher) {
+        let cmd = "diff file_1.txt file_2.txt -s --brief --expand-tabs --width=100";
+        let args = str_to_options(&cmd).into_iter().peekable();
+        bencher
+            .with_inputs(|| args.clone())
+            .bench_values(|data| black_box(params::parse_params(data)));
+    }
+}
+
+mod prepare {
+    use std::{
+        ffi::OsString,
+        fs::{self, File},
+        io::{BufWriter, Write},
+        path::Path,
+        sync::OnceLock,
+    };
+
+    use rand::RngExt;
+    use tempfile::TempDir;
+
+    use crate::{CHANGE_CHAR, FILE_SIZE_KILO_BYTES, NUM_DIFF, TEMP_DIR};
+
+    // file lines and .txt will be added
+    const FROM_FILE: &str = "from_file";
+    const TO_FILE: &str = "to_file";
+    const LINE_LENGTH: usize = 60;
+
+    /// Contains test data (file names) which only needs to be created once.
+    #[derive(Debug, Default)]
+    pub struct BenchContext {
+        pub tmp_dir: Option<TempDir>,
+        pub dir: String,
+        pub files_equal: Vec<(String, String)>,
+        pub files_different: Vec<(String, String)>,
+    }
+
+    impl BenchContext {
+        pub fn get_path(&self) -> &Path {
+            match &self.tmp_dir {
+                Some(tmp) => tmp.path(),
+                None => Path::new(&self.dir),
+            }
+        }
+
+        pub fn get_test_files_equal(&self, kb: u64) -> &(String, String) {
+            let p = FILE_SIZE_KILO_BYTES.iter().position(|f| *f == kb).unwrap();
+            &self.files_equal[p]
+        }
+
+        #[allow(unused)]
+        pub fn get_test_files_different(&self, kb: u64) -> &(String, String) {
+            let p = FILE_SIZE_KILO_BYTES.iter().position(|f| *f == kb).unwrap();
+            &self.files_different[p]
+        }
+    }
+
+    // Since each bench function is separate in Divan it is more difficult to dynamically create test data.
+    // This keeps the TempDir alive until the program exits and generates the files only once.
+    static SHARED_CONTEXT: OnceLock<BenchContext> = OnceLock::new();
+    /// Creates the test files once and provides them to all tests.
+    pub fn get_context() -> &'static BenchContext {
+        SHARED_CONTEXT.get_or_init(|| {
+            let mut ctx = BenchContext::default();
+            if TEMP_DIR.is_empty() {
+                let tmp_dir = TempDir::new().expect("Failed to create temp dir");
+                ctx.tmp_dir = Some(tmp_dir);
+            } else {
+                // uses current directory, the generated files are kept
+                let path = Path::new(TEMP_DIR);
+                if !path.exists() {
+                    fs::create_dir_all(path).expect("Path {path} could not be created");
+                }
+                ctx.dir = TEMP_DIR.to_string();
+            };
+
+            // generate test bytes
+            for kb in FILE_SIZE_KILO_BYTES {
+                let f = generate_test_files_bytes(ctx.get_path(), kb * 1000, 0, "eq")
+                    .expect("generate_test_files failed");
+                ctx.files_equal.push(f);
+                let f = generate_test_files_bytes(ctx.get_path(), kb * 1000, NUM_DIFF, "df")
+                    .expect("generate_test_files failed");
+                ctx.files_different.push(f);
+            }
+
+            ctx
+        })
+    }
+
+    pub fn str_to_options(opt: &str) -> Vec<OsString> {
+        let s: Vec<OsString> = opt
+            .split(" ")
+            .into_iter()
+            .filter(|s| !s.is_empty())
+            .map(|s| OsString::from(s))
+            .collect();
+
+        s
+    }
+
+    /// Generates two test files for comparison with <bytes> size.
+    ///
+    /// Each line consists of 10 words with 5 letters, giving a line length of 60 bytes.
+    /// If num_differences is set, '#' will be inserted between the first two words of a line,
+    /// evenly spaced in the file. 1 will add the change in the last line, so the comparison takes longest.
+    fn generate_test_files_bytes(
+        dir: &Path,
+        bytes: u64,
+        num_differences: u64,
+        id: &str,
+    ) -> std::io::Result<(String, String)> {
+        let id = if id.is_empty() {
+            "".to_string()
+        } else {
+            format!("{id}_")
+        };
+        let f1 = format!("{id}{FROM_FILE}_{bytes}.txt");
+        let f2 = format!("{id}{TO_FILE}_{bytes}.txt");
+        let from_path = dir.join(f1);
+        let to_path = dir.join(f2);
+
+        generate_file_bytes(&from_path, &to_path, bytes, num_differences)?;
+
+        Ok((
+            from_path.to_string_lossy().to_string(),
+            to_path.to_string_lossy().to_string(),
+        ))
+    }
+
+    fn generate_file_bytes(
+        from_name: &Path,
+        to_name: &Path,
+        bytes: u64,
+        num_differences: u64,
+    ) -> std::io::Result<()> {
+        let file_from = File::create(from_name)?;
+        let file_to = File::create(to_name)?;
+        // for int division, lines will be smaller than requested bytes
+        let n_lines = bytes / LINE_LENGTH as u64;
+        let change_every_n_lines = if num_differences == 0 {
+            0
+        } else {
+            let c = n_lines / num_differences;
+            if c == 0 {
+                1
+            } else {
+                c
+            }
+        };
+        // Use a larger 128KB buffer for massive files
+        let mut writer_from = BufWriter::with_capacity(128 * 1024, file_from);
+        let mut writer_to = BufWriter::with_capacity(128 * 1024, file_to);
+        let mut rng = rand::rng();
+
+        // Each line: (5 chars * 10 words) + 9 spaces + 1 newline = 60 bytes
+        let mut line_buffer = [b' '; 60];
+        line_buffer[59] = b'\n'; // Set the newline once at the end
+
+        for i in (0..n_lines).rev() {
+            // Fill only the letter positions, skipping spaces and the newline
+            for word_idx in 0..10 {
+                let start = word_idx * 6; // Each word + space block is 6 bytes
+                for i in 0..5 {
+                    line_buffer[start + i] = rng.random_range(b'a'..b'z' + 1);
+                }
+            }
+
+            // Write the raw bytes directly to both files
+            writer_from.write_all(&line_buffer)?;
+            // make changes in the file
+            if num_differences == 0 {
+                writer_to.write_all(&line_buffer)?;
+            } else {
+                if i % change_every_n_lines == 0 && n_lines - i > 2 {
+                    line_buffer[5] = CHANGE_CHAR;
+                }
+                writer_to.write_all(&line_buffer)?;
+                line_buffer[5] = b' ';
+            }
+        }
+
+        // create last line
+        let missing = (bytes - n_lines as u64 * LINE_LENGTH as u64) as usize;
+        if missing > 0 {
+            for word_idx in 0..10 {
+                let start = word_idx * 6; // Each word + space block is 6 bytes
+                for i in 0..5 {
+                    line_buffer[start + i] = rng.random_range(b'a'..b'z' + 1);
+                }
+            }
+            line_buffer[missing - 1] = b'\n';
+            writer_from.write_all(&line_buffer[0..missing])?;
+            writer_to.write_all(&line_buffer[0..missing])?;
+        }
+
+        writer_from.flush()?;
+        writer_to.flush()?;
+
+        Ok(())
+    }
+}
+
+mod binary {
+    use std::process::Command;
+
+    use crate::prepare::str_to_options;
+
+    pub fn bench_binary(program: &str, cmd_args: &str) -> std::process::ExitStatus {
+        let args = str_to_options(cmd_args);
+        Command::new(program)
+            .args(args)
+            .status()
+            .expect("Failed to execute binary")
+    }
+}
+
+fn main() {
+    // Run registered benchmarks.
+    divan::main();
+}
@@ -0,0 +1,15 @@
+[workspace]
+members = ["cargo:."]
+
+# Config for 'dist'
+[dist]
+# The preferred dist version to use in CI (Cargo.toml SemVer syntax)
+cargo-dist-version = "0.33.0"
+# CI backends to support
+ci = "github"
+# The installers to generate for each app
+installers = []
+# Target platforms to build apps for (Rust target-triple syntax)
+targets = ["aarch64-apple-darwin", "aarch64-unknown-linux-gnu", "x86_64-apple-darwin", "x86_64-unknown-linux-gnu", "x86_64-pc-windows-msvc"]
+# Skip checking whether the specified configuration files are up to date
+allow-dirty = ["ci"]
@@ -0,0 +1,6 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "config:recommended"
+  ]
+}
@@ -0,0 +1,998 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use std::collections::VecDeque;
+use std::io::Write;
+
+use crate::params::Params;
+use crate::utils::do_write_line;
+use crate::utils::get_modification_time;
+
+#[derive(Debug, PartialEq)]
+pub enum DiffLine {
+    Context(Vec<u8>),
+    Change(Vec<u8>),
+    Add(Vec<u8>),
+}
+
+#[derive(Debug, PartialEq)]
+struct Mismatch {
+    pub line_number_expected: usize,
+    pub line_number_actual: usize,
+    pub expected: Vec<DiffLine>,
+    pub actual: Vec<DiffLine>,
+    pub expected_missing_nl: bool,
+    pub actual_missing_nl: bool,
+    pub expected_all_context: bool,
+    pub actual_all_context: bool,
+}
+
+impl Mismatch {
+    fn new(line_number_expected: usize, line_number_actual: usize) -> Mismatch {
+        Mismatch {
+            line_number_expected,
+            line_number_actual,
+            expected: Vec::new(),
+            actual: Vec::new(),
+            expected_missing_nl: false,
+            actual_missing_nl: false,
+            expected_all_context: false,
+            actual_all_context: false,
+        }
+    }
+}
+
+/// A run of changed lines with no common line between them.
+struct ChangeBlock {
+    expected_start: usize,
+    actual_start: usize,
+    deletes: bool,
+    inserts: bool,
+}
+
+impl ChangeBlock {
+    fn new(mismatch: &Mismatch) -> Self {
+        Self {
+            expected_start: mismatch.expected.len(),
+            actual_start: mismatch.actual.len(),
+            deletes: false,
+            inserts: false,
+        }
+    }
+
+    /// Opens a block at the end of `mismatch` if none is open, and records
+    /// whether it deletes or inserts lines.
+    fn mark(block: &mut Option<Self>, mismatch: &Mismatch, deletes: bool, inserts: bool) {
+        let block = block.get_or_insert_with(|| Self::new(mismatch));
+        block.deletes |= deletes;
+        block.inserts |= inserts;
+    }
+
+    fn close(block: &mut Option<Self>, mismatch: &mut Mismatch) {
+        if let Some(block) = block.take() {
+            block.finish(mismatch);
+        }
+    }
+
+    /// Like GNU diff, a block that both deletes and inserts lines marks all of
+    /// them as changed (`!`), not only as many as pair up.
+    fn finish(self, mismatch: &mut Mismatch) {
+        if !(self.deletes && self.inserts) {
+            return;
+        }
+        let expected = mismatch.expected[self.expected_start..].iter_mut();
+        let actual = mismatch.actual[self.actual_start..].iter_mut();
+        for line in expected.chain(actual) {
+            if let DiffLine::Add(content) = line {
+                *line = DiffLine::Change(std::mem::take(content));
+            }
+        }
+    }
+}
+
+// Produces a diff between the expected output and actual output.
+fn make_diff(
+    expected: &[u8],
+    actual: &[u8],
+    context_size: usize,
+    stop_early: bool,
+) -> Vec<Mismatch> {
+    let mut line_number_expected = 1;
+    let mut line_number_actual = 1;
+    let mut context_queue: VecDeque<&[u8]> = VecDeque::with_capacity(context_size);
+    // Like GNU diff, keep changes in one hunk while at most twice the context
+    // size of unchanged lines separates them.
+    let max_gap = 2 * context_size;
+    let mut lines_since_mismatch = max_gap + 1;
+    let mut results = Vec::new();
+    let mut mismatch = Mismatch::new(0, 0);
+
+    let mut expected_lines: Vec<&[u8]> = expected.split(|&c| c == b'\n').collect();
+    let mut actual_lines: Vec<&[u8]> = actual.split(|&c| c == b'\n').collect();
+
+    debug_assert_eq!(b"".split(|&c| c == b'\n').count(), 1);
+    // ^ means that underflow here is impossible
+    let expected_lines_count = expected_lines.len() - 1;
+    let actual_lines_count = actual_lines.len() - 1;
+
+    if expected_lines.last() == Some(&&b""[..]) {
+        expected_lines.pop();
+    }
+
+    if actual_lines.last() == Some(&&b""[..]) {
+        actual_lines.pop();
+    }
+
+    let mut block: Option<ChangeBlock> = None;
+
+    for result in diff::slice(&expected_lines, &actual_lines) {
+        match result {
+            diff::Result::Left(str) => {
+                if lines_since_mismatch > max_gap {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(
+                        line_number_expected - context_queue.len(),
+                        line_number_actual - context_queue.len(),
+                    );
+                }
+
+                while let Some(line) = context_queue.pop_front() {
+                    mismatch.expected.push(DiffLine::Context(line.to_vec()));
+                    mismatch.actual.push(DiffLine::Context(line.to_vec()));
+                }
+
+                ChangeBlock::mark(&mut block, &mismatch, true, false);
+                mismatch.expected.push(DiffLine::Add(str.to_vec()));
+                if line_number_expected > expected_lines_count {
+                    mismatch.expected_missing_nl = true;
+                }
+                line_number_expected += 1;
+                lines_since_mismatch = 0;
+            }
+            diff::Result::Right(str) => {
+                if lines_since_mismatch > max_gap {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(
+                        line_number_expected - context_queue.len(),
+                        line_number_actual - context_queue.len(),
+                    );
+                }
+
+                while let Some(line) = context_queue.pop_front() {
+                    mismatch.expected.push(DiffLine::Context(line.to_vec()));
+                    mismatch.actual.push(DiffLine::Context(line.to_vec()));
+                }
+
+                ChangeBlock::mark(&mut block, &mismatch, false, true);
+                mismatch.actual.push(DiffLine::Add(str.to_vec()));
+                if line_number_actual > actual_lines_count {
+                    mismatch.actual_missing_nl = true;
+                }
+                line_number_actual += 1;
+                lines_since_mismatch = 0;
+            }
+            diff::Result::Both(str, _) => {
+                // if one of them is missing a newline and the other isn't, then they don't actually match
+                if (line_number_actual > actual_lines_count)
+                    && (line_number_expected > expected_lines_count)
+                {
+                    ChangeBlock::close(&mut block, &mut mismatch);
+                    if context_queue.len() < context_size {
+                        while let Some(line) = context_queue.pop_front() {
+                            mismatch.expected.push(DiffLine::Context(line.to_vec()));
+                            mismatch.actual.push(DiffLine::Context(line.to_vec()));
+                        }
+                        if lines_since_mismatch < context_size {
+                            mismatch.expected.push(DiffLine::Context(str.to_vec()));
+                            mismatch.actual.push(DiffLine::Context(str.to_vec()));
+                            mismatch.expected_missing_nl = true;
+                            mismatch.actual_missing_nl = true;
+                        }
+                    }
+                    lines_since_mismatch = 0;
+                } else if line_number_actual > actual_lines_count {
+                    if lines_since_mismatch > max_gap {
+                        results.push(mismatch);
+                        mismatch = Mismatch::new(
+                            line_number_expected - context_queue.len(),
+                            line_number_actual - context_queue.len(),
+                        );
+                    }
+                    while let Some(line) = context_queue.pop_front() {
+                        mismatch.expected.push(DiffLine::Context(line.to_vec()));
+                        mismatch.actual.push(DiffLine::Context(line.to_vec()));
+                    }
+                    ChangeBlock::mark(&mut block, &mismatch, true, true);
+                    mismatch.expected.push(DiffLine::Change(str.to_vec()));
+                    mismatch.actual.push(DiffLine::Change(str.to_vec()));
+                    mismatch.actual_missing_nl = true;
+                    lines_since_mismatch = 0;
+                } else if line_number_expected > expected_lines_count {
+                    if lines_since_mismatch > max_gap {
+                        results.push(mismatch);
+                        mismatch = Mismatch::new(
+                            line_number_expected - context_queue.len(),
+                            line_number_actual - context_queue.len(),
+                        );
+                    }
+                    while let Some(line) = context_queue.pop_front() {
+                        mismatch.expected.push(DiffLine::Context(line.to_vec()));
+                        mismatch.actual.push(DiffLine::Context(line.to_vec()));
+                    }
+                    ChangeBlock::mark(&mut block, &mismatch, true, true);
+                    mismatch.expected.push(DiffLine::Change(str.to_vec()));
+                    mismatch.expected_missing_nl = true;
+                    mismatch.actual.push(DiffLine::Change(str.to_vec()));
+                    lines_since_mismatch = 0;
+                } else {
+                    ChangeBlock::close(&mut block, &mut mismatch);
+                    debug_assert!(context_queue.len() <= context_size);
+                    if context_queue.len() >= context_size {
+                        let _ = context_queue.pop_front();
+                    }
+                    if lines_since_mismatch < context_size {
+                        mismatch.expected.push(DiffLine::Context(str.to_vec()));
+                        mismatch.actual.push(DiffLine::Context(str.to_vec()));
+                    } else if context_size > 0 {
+                        context_queue.push_back(str);
+                    }
+                    lines_since_mismatch += 1;
+                }
+                line_number_expected += 1;
+                line_number_actual += 1;
+            }
+        }
+        if stop_early && !results.is_empty() {
+            // Optimization: stop analyzing the files as soon as there are any differences
+            return results;
+        }
+    }
+
+    if let Some(block) = block {
+        block.finish(&mut mismatch);
+    }
+    results.push(mismatch);
+    results.remove(0);
+
+    if results.is_empty() && expected_lines_count != actual_lines_count {
+        let mut mismatch = Mismatch::new(expected_lines.len(), actual_lines.len());
+        // empty diff and only expected lines has a missing line at end
+        if expected_lines_count != expected_lines.len() {
+            mismatch.expected.push(DiffLine::Change(
+                expected_lines
+                    .pop()
+                    .expect("can't be empty; produced by split()")
+                    .to_vec(),
+            ));
+            mismatch.expected_missing_nl = true;
+            mismatch.actual.push(DiffLine::Change(
+                actual_lines
+                    .pop()
+                    .expect("can't be empty; produced by split()")
+                    .to_vec(),
+            ));
+            results.push(mismatch);
+        } else if actual_lines_count != actual_lines.len() {
+            mismatch.expected.push(DiffLine::Change(
+                expected_lines
+                    .pop()
+                    .expect("can't be empty; produced by split()")
+                    .to_vec(),
+            ));
+            mismatch.actual.push(DiffLine::Change(
+                actual_lines
+                    .pop()
+                    .expect("can't be empty; produced by split()")
+                    .to_vec(),
+            ));
+            mismatch.actual_missing_nl = true;
+            results.push(mismatch);
+        }
+    }
+
+    // hunks with pure context lines get truncated to empty
+    for mismatch in &mut results {
+        if !mismatch
+            .expected
+            .iter()
+            .any(|x| !matches!(&x, DiffLine::Context(_)))
+        {
+            mismatch.expected_all_context = true;
+        }
+        if !mismatch
+            .actual
+            .iter()
+            .any(|x| !matches!(&x, DiffLine::Context(_)))
+        {
+            mismatch.actual_all_context = true;
+        }
+    }
+
+    results
+}
+
+#[must_use]
+pub fn diff(expected: &[u8], actual: &[u8], params: &Params) -> Vec<u8> {
+    let from_modified_time = get_modification_time(&params.from.to_string_lossy());
+    let to_modified_time = get_modification_time(&params.to.to_string_lossy());
+    let mut output = format!(
+        "*** {0}\t{1}\n--- {2}\t{3}\n",
+        params.from.to_string_lossy(),
+        from_modified_time,
+        params.to.to_string_lossy(),
+        to_modified_time
+    )
+    .into_bytes();
+    let diff_results = make_diff(expected, actual, params.context_count, params.brief);
+    if diff_results.is_empty() {
+        return Vec::new();
+    }
+    if params.brief {
+        return output;
+    }
+    for result in diff_results {
+        let mut line_number_expected = result.line_number_expected;
+        let mut line_number_actual = result.line_number_actual;
+        let mut expected_count = result.expected.len();
+        let mut actual_count = result.actual.len();
+        if expected_count == 0 {
+            line_number_expected -= 1;
+            expected_count = 1;
+        }
+        if actual_count == 0 {
+            line_number_actual -= 1;
+            actual_count = 1;
+        }
+        let end_line_number_expected = expected_count + line_number_expected - 1;
+        let end_line_number_actual = actual_count + line_number_actual - 1;
+        let exp_start = if end_line_number_expected == line_number_expected {
+            String::new()
+        } else {
+            format!("{line_number_expected},")
+        };
+        let act_start = if end_line_number_actual == line_number_actual {
+            String::new()
+        } else {
+            format!("{line_number_actual},")
+        };
+        writeln!(
+            output,
+            "***************\n*** {exp_start}{end_line_number_expected} ****"
+        )
+        .expect("write to Vec is infallible");
+        if !result.expected_all_context {
+            for line in result.expected {
+                match line {
+                    DiffLine::Context(e) => {
+                        write!(output, "  ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                    DiffLine::Change(e) => {
+                        write!(output, "! ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                    DiffLine::Add(e) => {
+                        write!(output, "- ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                }
+            }
+            if result.expected_missing_nl {
+                writeln!(output, r"\ No newline at end of file")
+                    .expect("write to Vec is infallible");
+            }
+        }
+        writeln!(output, "--- {act_start}{end_line_number_actual} ----")
+            .expect("write to Vec is infallible");
+        if !result.actual_all_context {
+            for line in result.actual {
+                match line {
+                    DiffLine::Context(e) => {
+                        write!(output, "  ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                    DiffLine::Change(e) => {
+                        write!(output, "! ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                    DiffLine::Add(e) => {
+                        write!(output, "+ ").expect("write to Vec is infallible");
+                        do_write_line(&mut output, &e, params.expand_tabs, params.tabsize)
+                            .expect("write to Vec is infallible");
+                        writeln!(output).unwrap();
+                    }
+                }
+            }
+            if result.actual_missing_nl {
+                writeln!(output, r"\ No newline at end of file")
+                    .expect("write to Vec is infallible");
+            }
+        }
+    }
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    use crate::utils::testcmds::PATCH_CMD;
+
+    #[test]
+    fn test_permutations() {
+        // test all possible six-line files.
+        let target = "target/context-diff/";
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"b\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"e\n" } else { b"f\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"g\n" } else { b"h\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"i\n" } else { b"j\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"k\n" } else { b"l\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let patched = &format!("{target}/alef");
+                                let diff = diff(
+                                    &alef,
+                                    &bet,
+                                    &Params {
+                                        from: patched.into(),
+                                        to: patched.into(),
+                                        context_count: 2,
+                                        ..Default::default()
+                                    },
+                                );
+                                File::create(format!("{target}/ab.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg("--context")
+                                    .stdin(File::open(format!("{target}/ab.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alef")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_empty_lines() {
+        let target = "target/context-diff/";
+        // test all possible six-line files with missing newlines.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"\n" } else { b"b\n" }).unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"\n" } else { b"d\n" }).unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"\n" } else { b"f\n" }).unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"\n" } else { b"h\n" }).unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"\n" } else { b"j\n" }).unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"\n" } else { b"l\n" }).unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let patched = &format!("{target}/alef_");
+                                let diff = diff(
+                                    &alef,
+                                    &bet,
+                                    &Params {
+                                        from: patched.into(),
+                                        to: patched.into(),
+                                        context_count: 2,
+                                        ..Default::default()
+                                    },
+                                );
+                                File::create(format!("{target}/ab_.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef_")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet_")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg("--context")
+                                    .stdin(File::open(format!("{target}/ab_.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alef_")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_missing_lines() {
+        let target = "target/context-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"" }).unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"c\n" } else { b"" }).unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"e\n" } else { b"" }).unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"g\n" } else { b"" }).unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"i\n" } else { b"" }).unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"k\n" } else { b"" }).unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                if alef.is_empty() && bet.is_empty() {
+                                    continue;
+                                };
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let patched = &format!("{target}/alefx");
+                                let diff = diff(
+                                    &alef,
+                                    &bet,
+                                    &Params {
+                                        from: patched.into(),
+                                        to: patched.into(),
+                                        context_count: 2,
+                                        ..Default::default()
+                                    },
+                                );
+                                File::create(format!("{target}/abx.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alefx")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/betx")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg("--context")
+                                    .stdin(File::open(format!("{target}/abx.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alefx")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_reverse() {
+        let target = "target/context-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"f\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"a\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"b\n" } else { b"e\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"c\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"d\n" } else { b"c\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"e\n" } else { b"b\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"e\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"f\n" } else { b"a\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let alefr_path = &format!("{target}/alefr");
+                                let diff = diff(
+                                    &alef,
+                                    &bet,
+                                    &Params {
+                                        from: alefr_path.into(),
+                                        to: alefr_path.into(),
+                                        context_count: 2,
+                                        ..Default::default()
+                                    },
+                                );
+                                File::create(format!("{target}/abr.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alefr")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/betr")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg("--context")
+                                    .stdin(File::open(format!("{target}/abr.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alefr")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_stop_early() {
+        use crate::assert_diff_eq;
+
+        let from_filename = "foo";
+        let from = ["a", "b", "c", ""].join("\n");
+        let to_filename = "bar";
+        let to = ["a", "d", "c", ""].join("\n");
+
+        let diff_full = diff(
+            from.as_bytes(),
+            to.as_bytes(),
+            &Params {
+                from: from_filename.into(),
+                to: to_filename.into(),
+                ..Default::default()
+            },
+        );
+
+        let expected_full = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 1,3 ****",
+            "  a",
+            "! b",
+            "  c",
+            "--- 1,3 ----",
+            "  a",
+            "! d",
+            "  c",
+            "",
+        ]
+        .join("\n");
+        assert_diff_eq!(diff_full, expected_full);
+
+        let diff_brief = diff(
+            from.as_bytes(),
+            to.as_bytes(),
+            &Params {
+                from: from_filename.into(),
+                to: to_filename.into(),
+                brief: true,
+                ..Default::default()
+            },
+        );
+
+        let expected_brief = ["*** foo\tTIMESTAMP", "--- bar\tTIMESTAMP", ""].join("\n");
+        assert_diff_eq!(diff_brief, expected_brief);
+
+        let nodiff_full = diff(
+            from.as_bytes(),
+            from.as_bytes(),
+            &Params {
+                from: from_filename.into(),
+                to: to_filename.into(),
+                ..Default::default()
+            },
+        );
+        assert!(nodiff_full.is_empty());
+
+        let nodiff_brief = diff(
+            from.as_bytes(),
+            from.as_bytes(),
+            &Params {
+                from: from_filename.into(),
+                to: to_filename.into(),
+                brief: true,
+                ..Default::default()
+            },
+        );
+        assert!(nodiff_brief.is_empty());
+    }
+
+    #[test]
+    fn test_change_block_lines_all_changed() {
+        use crate::assert_diff_eq;
+
+        let params = Params {
+            from: "foo".into(),
+            to: "bar".into(),
+            ..Default::default()
+        };
+
+        // Two lines replaced by one: both old lines are changed, not one deleted.
+        let from = ["a", "b", "c", "d", ""].join("\n");
+        let to = ["a", "x", "d", ""].join("\n");
+        let expected = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 1,4 ****",
+            "  a",
+            "! b",
+            "! c",
+            "  d",
+            "--- 1,3 ----",
+            "  a",
+            "! x",
+            "  d",
+            "",
+        ]
+        .join("\n");
+        let output = diff(from.as_bytes(), to.as_bytes(), &params);
+        assert_diff_eq!(output, expected);
+
+        // One line replaced by three: all three new lines are changed.
+        let from = ["a", "b", ""].join("\n");
+        let to = ["a", "x", "y", "z", ""].join("\n");
+        let expected = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 1,2 ****",
+            "  a",
+            "! b",
+            "--- 1,4 ----",
+            "  a",
+            "! x",
+            "! y",
+            "! z",
+            "",
+        ]
+        .join("\n");
+        let output = diff(from.as_bytes(), to.as_bytes(), &params);
+        assert_diff_eq!(output, expected);
+    }
+
+    #[test]
+    fn test_hunk_merging() {
+        use crate::assert_diff_eq;
+
+        let params = Params {
+            from: "foo".into(),
+            to: "bar".into(),
+            context_count: 1,
+            ..Default::default()
+        };
+
+        // Changes separated by up to twice the context size share one hunk.
+        let from = ["a", "b", "c", "d", "e", "f", ""].join("\n");
+        let to = ["a", "B", "c", "d", "E", "f", ""].join("\n");
+        let expected = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 1,6 ****",
+            "  a",
+            "! b",
+            "  c",
+            "  d",
+            "! e",
+            "  f",
+            "--- 1,6 ----",
+            "  a",
+            "! B",
+            "  c",
+            "  d",
+            "! E",
+            "  f",
+            "",
+        ]
+        .join("\n");
+        let output = diff(from.as_bytes(), to.as_bytes(), &params);
+        assert_diff_eq!(output, expected);
+
+        // One more unchanged line between them splits the hunk.
+        let from = ["a", "b", "c", "d", "e", "f", "g", ""].join("\n");
+        let to = ["a", "B", "c", "d", "e", "F", "g", ""].join("\n");
+        let expected = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 1,3 ****",
+            "  a",
+            "! b",
+            "  c",
+            "--- 1,3 ----",
+            "  a",
+            "! B",
+            "  c",
+            "***************",
+            "*** 5,7 ****",
+            "  e",
+            "! f",
+            "  g",
+            "--- 5,7 ----",
+            "  e",
+            "! F",
+            "  g",
+            "",
+        ]
+        .join("\n");
+        let output = diff(from.as_bytes(), to.as_bytes(), &params);
+        assert_diff_eq!(output, expected);
+
+        // An insertion before a nearby change gives the two sides different
+        // line counts; the hunks must still be merged (issue #268).
+        let from = ["milk", "eggs", "bread", "butter", "apples", ""].join("\n");
+        let to = ["milk", "eggs", "yogurt", "bread", "honey", "apples", ""].join("\n");
+        let expected = [
+            "*** foo\tTIMESTAMP",
+            "--- bar\tTIMESTAMP",
+            "***************",
+            "*** 2,5 ****",
+            "  eggs",
+            "  bread",
+            "! butter",
+            "  apples",
+            "--- 2,6 ----",
+            "  eggs",
+            "+ yogurt",
+            "  bread",
+            "! honey",
+            "  apples",
+            "",
+        ]
+        .join("\n");
+        let output = diff(from.as_bytes(), to.as_bytes(), &params);
+        assert_diff_eq!(output, expected);
+    }
+}
@@ -0,0 +1,151 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use crate::params::{parse_params, Format};
+use crate::utils::report_failure_to_read_input_file;
+use crate::{context_diff, ed_diff, normal_diff, side_diff, unified_diff};
+use std::env::ArgsOs;
+use std::ffi::OsString;
+use std::fs;
+use std::io::{self, stdout, Read, Write};
+use std::iter::Peekable;
+use std::process::{exit, ExitCode};
+
+// Exit codes are documented at
+// https://www.gnu.org/software/diffutils/manual/html_node/Invoking-diff.html.
+//     An exit status of 0 means no differences were found,
+//     1 means some differences were found,
+//     and 2 means trouble.
+pub fn main(opts: Peekable<ArgsOs>) -> ExitCode {
+    let params = parse_params(opts).unwrap_or_else(|error| {
+        eprintln!("{error}");
+        exit(2);
+    });
+    if params.recursive {
+        return recursive(&params).unwrap_or_else(|error| {
+            eprintln!("diff: {error}");
+            ExitCode::from(2)
+        });
+    }
+    compare(&params)
+}
+
+/// Compare directory entries in lexical order, with GNU diff's recursive output.
+fn recursive(params: &crate::params::Params) -> io::Result<ExitCode> {
+    let from = std::path::Path::new(&params.from);
+    let to = std::path::Path::new(&params.to);
+    if !from.is_dir() || !to.is_dir() {
+        if fs::read(from)? != fs::read(to)? {
+            println!("diff -r {} {}", from.display(), to.display());
+        }
+        return Ok(compare(params));
+    }
+    let mut names = std::collections::BTreeSet::new();
+    for dir in [from, to] {
+        for entry in fs::read_dir(dir)? { names.insert(entry?.file_name()); }
+    }
+    let mut status = ExitCode::SUCCESS;
+    for name in names {
+        let left = from.join(&name);
+        let right = to.join(&name);
+        let result = if !left.exists() || !right.exists() {
+            let parent = if left.exists() { from } else { to };
+            println!("Only in {}: {}", parent.display(), name.to_string_lossy());
+            ExitCode::from(1)
+        } else if left.is_dir() != right.is_dir() {
+            println!("File {} is a {} while file {} is a {}", left.display(),
+                if left.is_dir() { "directory" } else { "regular file" }, right.display(),
+                if right.is_dir() { "directory" } else { "regular file" });
+            ExitCode::from(1)
+        } else {
+            let mut child = params.clone();
+            child.from = left.into_os_string();
+            child.to = right.into_os_string();
+            recursive(&child)?
+        };
+        if result == ExitCode::from(2) { status = result; }
+        else if result == ExitCode::from(1) && status == ExitCode::SUCCESS { status = result; }
+    }
+    Ok(status)
+}
+
+fn compare(params: &crate::params::Params) -> ExitCode {
+    // if from and to are the same file, no need to perform any comparison
+    let maybe_report_identical_files = || {
+        if params.report_identical_files {
+            println!(
+                "Files {} and {} are identical",
+                params.from.to_string_lossy(),
+                params.to.to_string_lossy(),
+            );
+        }
+    };
+    if params.from == "-" && params.to == "-"
+        || same_file::is_same_file(&params.from, &params.to).unwrap_or(false)
+    {
+        maybe_report_identical_files();
+        return ExitCode::SUCCESS;
+    }
+
+    // read files
+    fn read_file_contents(filepath: &OsString) -> io::Result<Vec<u8>> {
+        if filepath == "-" {
+            let mut content = Vec::new();
+            io::stdin().read_to_end(&mut content).and(Ok(content))
+        } else {
+            fs::read(filepath)
+        }
+    }
+    let mut io_error = false;
+    let from_content = match read_file_contents(&params.from) {
+        Ok(from_content) => from_content,
+        Err(e) => {
+            report_failure_to_read_input_file(&params.executable, &params.from, &e);
+            io_error = true;
+            vec![]
+        }
+    };
+    let to_content = match read_file_contents(&params.to) {
+        Ok(to_content) => to_content,
+        Err(e) => {
+            report_failure_to_read_input_file(&params.executable, &params.to, &e);
+            io_error = true;
+            vec![]
+        }
+    };
+    if io_error {
+        return ExitCode::from(2);
+    }
+
+    // run diff
+    let result: Vec<u8> = match params.format {
+        Format::Normal => normal_diff::diff(&from_content, &to_content, &params),
+        Format::Unified => unified_diff::diff(&from_content, &to_content, &params),
+        Format::Context => context_diff::diff(&from_content, &to_content, &params),
+        Format::Ed => ed_diff::diff(&from_content, &to_content, &params).unwrap_or_else(|error| {
+            eprintln!("{error}");
+            exit(2);
+        }),
+        Format::SideBySide => {
+            let mut output = stdout().lock();
+            side_diff::diff(&from_content, &to_content, &mut output, &params)
+        }
+    };
+    if params.brief && !result.is_empty() {
+        println!(
+            "Files {} and {} differ",
+            params.from.to_string_lossy(),
+            params.to.to_string_lossy()
+        );
+    } else {
+        io::stdout().write_all(&result).unwrap();
+    }
+    if result.is_empty() {
+        maybe_report_identical_files();
+        ExitCode::SUCCESS
+    } else {
+        ExitCode::from(1)
+    }
+}
@@ -0,0 +1,452 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use std::io::Write;
+
+use crate::params::Params;
+use crate::utils::do_write_line;
+
+#[derive(Debug, PartialEq)]
+struct Mismatch {
+    pub line_number_expected: usize,
+    pub line_number_actual: usize,
+    pub expected: Vec<Vec<u8>>,
+    pub actual: Vec<Vec<u8>>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum DiffError {
+    MissingNL,
+}
+
+impl std::fmt::Display for DiffError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        std::fmt::Display::fmt("No newline at end of file", f)
+    }
+}
+
+impl From<DiffError> for String {
+    fn from(_: DiffError) -> String {
+        "No newline at end of file".into()
+    }
+}
+
+impl Mismatch {
+    fn new(line_number_expected: usize, line_number_actual: usize) -> Mismatch {
+        Mismatch {
+            line_number_expected,
+            line_number_actual,
+            expected: Vec::new(),
+            actual: Vec::new(),
+        }
+    }
+}
+
+// Produces a diff between the expected output and actual output.
+fn make_diff(expected: &[u8], actual: &[u8], stop_early: bool) -> Result<Vec<Mismatch>, DiffError> {
+    let mut line_number_expected = 1;
+    let mut line_number_actual = 1;
+    let mut results = Vec::new();
+    let mut mismatch = Mismatch::new(line_number_expected, line_number_actual);
+
+    let mut expected_lines: Vec<&[u8]> = expected.split(|&c| c == b'\n').collect();
+    let mut actual_lines: Vec<&[u8]> = actual.split(|&c| c == b'\n').collect();
+
+    debug_assert_eq!(b"".split(|&c| c == b'\n').count(), 1);
+    // ^ means that underflow here is impossible
+    let _expected_lines_count = expected_lines.len() - 1;
+    let _actual_lines_count = actual_lines.len() - 1;
+
+    if expected_lines.last() == Some(&&b""[..]) {
+        expected_lines.pop();
+    } else {
+        return Err(DiffError::MissingNL);
+    }
+
+    if actual_lines.last() == Some(&&b""[..]) {
+        actual_lines.pop();
+    } else {
+        return Err(DiffError::MissingNL);
+    }
+
+    for result in diff::slice(&expected_lines, &actual_lines) {
+        match result {
+            diff::Result::Left(str) => {
+                if !mismatch.actual.is_empty() {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(line_number_expected, line_number_actual);
+                }
+                mismatch.expected.push(str.to_vec());
+                line_number_expected += 1;
+            }
+            diff::Result::Right(str) => {
+                mismatch.actual.push(str.to_vec());
+                line_number_actual += 1;
+            }
+            diff::Result::Both(_str, _) => {
+                line_number_expected += 1;
+                line_number_actual += 1;
+                if !mismatch.actual.is_empty() || !mismatch.expected.is_empty() {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(line_number_expected, line_number_actual);
+                } else {
+                    mismatch.line_number_expected = line_number_expected;
+                    mismatch.line_number_actual = line_number_actual;
+                }
+            }
+        }
+        if stop_early && !results.is_empty() {
+            // Optimization: stop analyzing the files as soon as there are any differences
+            return Ok(results);
+        }
+    }
+
+    if !mismatch.actual.is_empty() || !mismatch.expected.is_empty() {
+        results.push(mismatch);
+    }
+
+    Ok(results)
+}
+
+pub fn diff(expected: &[u8], actual: &[u8], params: &Params) -> Result<Vec<u8>, DiffError> {
+    let mut output = Vec::new();
+    let diff_results = make_diff(expected, actual, params.brief)?;
+    if params.brief && !diff_results.is_empty() {
+        write!(&mut output, "\0").unwrap();
+        return Ok(output);
+    }
+    let mut lines_offset = 0;
+    for result in diff_results {
+        let line_number_expected: isize = result.line_number_expected as isize + lines_offset;
+        let _line_number_actual: isize = result.line_number_actual as isize + lines_offset;
+        let expected_count: isize = result.expected.len() as isize;
+        let actual_count: isize = result.actual.len() as isize;
+        match (expected_count, actual_count) {
+            (0, 0) => unreachable!(),
+            (0, _) => writeln!(&mut output, "{}a", line_number_expected - 1).unwrap(),
+            (_, 0) => writeln!(
+                &mut output,
+                "{},{}d",
+                line_number_expected,
+                expected_count + line_number_expected - 1
+            )
+            .unwrap(),
+            (1, _) => writeln!(&mut output, "{line_number_expected}c").unwrap(),
+            _ => writeln!(
+                &mut output,
+                "{},{}c",
+                line_number_expected,
+                expected_count + line_number_expected - 1
+            )
+            .unwrap(),
+        }
+        lines_offset += actual_count - expected_count;
+        if actual_count != 0 {
+            for actual in &result.actual {
+                if actual == b"." {
+                    writeln!(&mut output, "..\n.\ns/.//\na").unwrap();
+                } else {
+                    do_write_line(&mut output, actual, params.expand_tabs, params.tabsize).unwrap();
+                    writeln!(&mut output).unwrap();
+                }
+            }
+            writeln!(&mut output, ".").unwrap();
+        }
+    }
+    Ok(output)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    use crate::utils::testcmds::ED_CMD;
+
+    pub fn diff_w(expected: &[u8], actual: &[u8], filename: &str) -> Result<Vec<u8>, DiffError> {
+        let mut output = diff(expected, actual, &Params::default())?;
+        writeln!(&mut output, "w {filename}").unwrap();
+        Ok(output)
+    }
+
+    #[test]
+    fn test_basic() {
+        let from = b"a\n";
+        let to = b"b\n";
+        let diff = diff(from, to, &Params::default()).unwrap();
+        let expected = ["1c", "b", ".", ""].join("\n");
+        assert_eq!(diff, expected.as_bytes());
+    }
+
+    #[test]
+    fn test_permutations() {
+        let target = "target/ed-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::File;
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"b\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"e\n" } else { b"f\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"g\n" } else { b"h\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"i\n" } else { b"j\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"k\n" } else { b"l\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff_w(&alef, &bet, &format!("{target}/alef")).unwrap();
+                                File::create(format!("{target}/ab.ed"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                #[cfg(not(windows))] // there's no ed on windows
+                                {
+                                    let output = ED_CMD
+                                        .new()
+                                        .arg(format!("{target}/alef"))
+                                        .stdin(File::open(format!("{target}/ab.ed")).unwrap())
+                                        .output()
+                                        .unwrap();
+                                    assert!(output.status.success(), "{output:?}");
+                                    //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                    //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                    let alef = std::fs::read(format!("{target}/alef")).unwrap();
+                                    assert_eq!(alef, bet);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_empty_lines() {
+        let target = "target/ed-diff/";
+        // test all possible six-line files with missing newlines.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::File;
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"\n" } else { b"b\n" }).unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"\n" } else { b"d\n" }).unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"\n" } else { b"f\n" }).unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"\n" } else { b"h\n" }).unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"\n" } else { b"j\n" }).unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"\n" } else { b"l\n" }).unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff_w(&alef, &bet, &format!("{target}/alef_")).unwrap();
+                                File::create(format!("{target}/ab_.ed"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef_")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet_")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                #[cfg(not(windows))] // there's no ed on windows
+                                {
+                                    let output = ED_CMD
+                                        .new()
+                                        .arg(format!("{target}/alef_"))
+                                        .stdin(File::open(format!("{target}/ab_.ed")).unwrap())
+                                        .output()
+                                        .unwrap();
+                                    assert!(output.status.success(), "{output:?}");
+                                    //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                    //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                    let alef = std::fs::read(format!("{target}/alef_")).unwrap();
+                                    assert_eq!(alef, bet);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_reverse() {
+        let target = "target/ed-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::File;
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"f\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"a\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"b\n" } else { b"e\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"c\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"d\n" } else { b"c\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"e\n" } else { b"b\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"e\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"f\n" } else { b"a\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff_w(&alef, &bet, &format!("{target}/alefr")).unwrap();
+                                File::create(format!("{target}/abr.ed"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alefr")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/betr")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                #[cfg(not(windows))] // there's no ed on windows
+                                {
+                                    let output = ED_CMD
+                                        .new()
+                                        .arg(format!("{target}/alefr"))
+                                        .stdin(File::open(format!("{target}/abr.ed")).unwrap())
+                                        .output()
+                                        .unwrap();
+                                    assert!(output.status.success(), "{output:?}");
+                                    //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                    //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                    let alef = std::fs::read(format!("{target}/alefr")).unwrap();
+                                    assert_eq!(alef, bet);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_stop_early() {
+        let from = ["a", "b", "c", ""].join("\n");
+        let to = ["a", "d", "c", ""].join("\n");
+
+        let diff_full = diff(from.as_bytes(), to.as_bytes(), &Params::default()).unwrap();
+        let expected_full = ["2c", "d", ".", ""].join("\n");
+        assert_eq!(diff_full, expected_full.as_bytes());
+
+        let diff_brief = diff(
+            from.as_bytes(),
+            to.as_bytes(),
+            &Params {
+                brief: true,
+                ..Default::default()
+            },
+        )
+        .unwrap();
+        let expected_brief = "\0".as_bytes();
+        assert_eq!(diff_brief, expected_brief);
+
+        let nodiff_full = diff(from.as_bytes(), from.as_bytes(), &Params::default()).unwrap();
+        assert!(nodiff_full.is_empty());
+
+        let nodiff_brief = diff(
+            from.as_bytes(),
+            from.as_bytes(),
+            &Params {
+                brief: true,
+                ..Default::default()
+            },
+        )
+        .unwrap();
+        assert!(nodiff_brief.is_empty());
+    }
+}
@@ -0,0 +1,16 @@
+pub mod cmp;
+pub mod context_diff;
+pub mod ed_diff;
+pub mod macros;
+pub mod normal_diff;
+pub mod params;
+pub mod side_diff;
+pub mod unified_diff;
+pub mod utils;
+
+// Re-export the public functions/types you need
+pub use context_diff::diff as context_diff;
+pub use ed_diff::diff as ed_diff;
+pub use normal_diff::diff as normal_diff;
+pub use side_diff::diff as side_by_side_diff;
+pub use unified_diff::diff as unified_diff;
@@ -0,0 +1,25 @@
+// asserts equality of the actual diff and expected diff
+// considering datetime varitations
+//
+// It replaces the modification time in the actual diff
+// with placeholder "TIMESTAMP" and then asserts the equality
+//
+// For eg.
+// let brief = "*** fruits_old.txt\t2024-03-24 23:43:05.189597645 +0530\n
+//              --- fruits_new.txt\t2024-03-24 23:35:08.922581904 +0530\n";
+//
+// replaced = "*** fruits_old.txt\tTIMESTAMP\n
+//             --- fruits_new.txt\tTIMESTAMP\n";
+#[macro_export]
+macro_rules! assert_diff_eq {
+    ($actual:expr, $expected:expr) => {{
+        use regex::Regex;
+        use std::str;
+
+        let diff = str::from_utf8(&$actual).unwrap();
+        let re = Regex::new(r"\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d+ [+-]\d{4}").unwrap();
+        let actual = re.replacen(diff, 2, "TIMESTAMP");
+
+        assert_eq!(actual, $expected);
+    }};
+}
@@ -0,0 +1,85 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use std::{
+    env::ArgsOs,
+    ffi::{OsStr, OsString},
+    iter::Peekable,
+    path::{Path, PathBuf},
+    process::ExitCode,
+};
+
+mod cmp;
+mod context_diff;
+mod diff;
+mod ed_diff;
+mod macros;
+mod normal_diff;
+mod params;
+mod side_diff;
+mod unified_diff;
+mod utils;
+
+/// # Panics
+/// Panics if the binary path cannot be determined
+fn binary_path(args: &mut Peekable<ArgsOs>) -> PathBuf {
+    match args.peek() {
+        Some(ref s) if !s.is_empty() => PathBuf::from(s),
+        _ => std::env::current_exe().unwrap(),
+    }
+}
+
+/// #Panics
+/// Panics if path has no UTF-8 valid name
+fn name(binary_path: &Path) -> &OsStr {
+    binary_path.file_stem().unwrap()
+}
+
+const VERSION: &str = env!("CARGO_PKG_VERSION");
+
+fn usage(name: &str) {
+    println!("{name} {VERSION} (multi-call binary)\n");
+    println!("Usage: {name} [function [arguments...]]\n");
+    println!("Currently defined functions:\n");
+    println!("    cmp, diff\n");
+}
+
+fn second_arg_error(name: &OsStr) -> ! {
+    eprintln!("Expected utility name as second argument, got nothing.");
+    usage(&name.to_string_lossy());
+    std::process::exit(0);
+}
+
+fn main() -> ExitCode {
+    let mut args = std::env::args_os().peekable();
+
+    let exe_path = binary_path(&mut args);
+    let exe_name = name(&exe_path);
+
+    let util_name = if exe_name.as_encoded_bytes().ends_with(b"diffutils") {
+        // Discard the item we peeked.
+        let _ = args.next();
+
+        args.peek()
+            .cloned()
+            .unwrap_or_else(|| second_arg_error(exe_name))
+    } else {
+        OsString::from(exe_name)
+    };
+
+    match util_name.as_encoded_bytes() {
+        name if name.ends_with(b"diff") => diff::main(args),
+        name if name.ends_with(b"cmp") => cmp::main(args),
+        name => {
+            use std::io::{stderr, Write as _};
+            let _ = writeln!(
+                stderr(),
+                "{}: utility not supported",
+                String::from_utf8_lossy(name)
+            );
+            ExitCode::from(2)
+        }
+    }
+}
@@ -0,0 +1,586 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use std::io::Write;
+
+use crate::params::Params;
+use crate::utils::do_write_line;
+
+#[derive(Debug, PartialEq)]
+struct Mismatch {
+    pub line_number_expected: usize,
+    pub line_number_actual: usize,
+    pub expected: Vec<Vec<u8>>,
+    pub actual: Vec<Vec<u8>>,
+    pub expected_missing_nl: bool,
+    pub actual_missing_nl: bool,
+}
+
+impl Mismatch {
+    fn new(line_number_expected: usize, line_number_actual: usize) -> Mismatch {
+        Mismatch {
+            line_number_expected,
+            line_number_actual,
+            expected: Vec::new(),
+            actual: Vec::new(),
+            expected_missing_nl: false,
+            actual_missing_nl: false,
+        }
+    }
+}
+
+// Produces a diff between the expected output and actual output.
+fn make_diff(expected: &[u8], actual: &[u8], stop_early: bool) -> Vec<Mismatch> {
+    let mut line_number_expected = 1;
+    let mut line_number_actual = 1;
+    let mut results = Vec::new();
+    let mut mismatch = Mismatch::new(line_number_expected, line_number_actual);
+
+    let mut expected_lines: Vec<&[u8]> = expected.split(|&c| c == b'\n').collect();
+    let mut actual_lines: Vec<&[u8]> = actual.split(|&c| c == b'\n').collect();
+
+    debug_assert_eq!(b"".split(|&c| c == b'\n').count(), 1);
+    // ^ means that underflow here is impossible
+    let expected_lines_count = expected_lines.len() - 1;
+    let actual_lines_count = actual_lines.len() - 1;
+
+    if expected_lines.last() == Some(&&b""[..]) {
+        expected_lines.pop();
+    }
+
+    if actual_lines.last() == Some(&&b""[..]) {
+        actual_lines.pop();
+    }
+
+    for result in diff::slice(&expected_lines, &actual_lines) {
+        match result {
+            diff::Result::Left(str) => {
+                if !mismatch.actual.is_empty() && !mismatch.actual_missing_nl {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(line_number_expected, line_number_actual);
+                }
+                mismatch.expected.push(str.to_vec());
+                mismatch.expected_missing_nl = line_number_expected > expected_lines_count;
+                line_number_expected += 1;
+            }
+            diff::Result::Right(str) => {
+                mismatch.actual.push(str.to_vec());
+                mismatch.actual_missing_nl = line_number_actual > actual_lines_count;
+                line_number_actual += 1;
+            }
+            diff::Result::Both(str, _) => {
+                match (
+                    line_number_expected > expected_lines_count,
+                    line_number_actual > actual_lines_count,
+                ) {
+                    (true, false) => {
+                        line_number_expected += 1;
+                        line_number_actual += 1;
+                        mismatch.expected.push(str.to_vec());
+                        mismatch.expected_missing_nl = true;
+                        mismatch.actual.push(str.to_vec());
+                    }
+                    (false, true) => {
+                        line_number_expected += 1;
+                        line_number_actual += 1;
+                        mismatch.actual.push(str.to_vec());
+                        mismatch.actual_missing_nl = true;
+                        mismatch.expected.push(str.to_vec());
+                    }
+                    (true, true) | (false, false) => {
+                        line_number_expected += 1;
+                        line_number_actual += 1;
+                        if !mismatch.actual.is_empty() || !mismatch.expected.is_empty() {
+                            results.push(mismatch);
+                            mismatch = Mismatch::new(line_number_expected, line_number_actual);
+                        } else {
+                            mismatch.line_number_expected = line_number_expected;
+                            mismatch.line_number_actual = line_number_actual;
+                        }
+                    }
+                }
+            }
+        }
+        if stop_early && !results.is_empty() {
+            // Optimization: stop analyzing the files as soon as there are any differences
+            return results;
+        }
+    }
+
+    if !mismatch.actual.is_empty() || !mismatch.expected.is_empty() {
+        results.push(mismatch);
+    }
+
+    results
+}
+
+#[must_use]
+pub fn diff(expected: &[u8], actual: &[u8], params: &Params) -> Vec<u8> {
+    // See https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Normal.html
+    // for details on the syntax of the normal format.
+    let mut output = Vec::new();
+    let diff_results = make_diff(expected, actual, params.brief);
+    if params.brief && !diff_results.is_empty() {
+        write!(&mut output, "\0").unwrap();
+        return output;
+    }
+    for result in diff_results {
+        let line_number_expected = result.line_number_expected;
+        let line_number_actual = result.line_number_actual;
+        let expected_count = result.expected.len();
+        let actual_count = result.actual.len();
+        match (expected_count, actual_count) {
+            (0, 0) => unreachable!(),
+            (0, _) => writeln!(
+                // 'a' stands for "Add lines"
+                &mut output,
+                "{}a{},{}",
+                line_number_expected - 1,
+                line_number_actual,
+                line_number_actual + actual_count - 1
+            )
+            .unwrap(),
+            (_, 0) => writeln!(
+                // 'd' stands for "Delete lines"
+                &mut output,
+                "{},{}d{}",
+                line_number_expected,
+                expected_count + line_number_expected - 1,
+                line_number_actual - 1
+            )
+            .unwrap(),
+            (1, 1) => writeln!(
+                // 'c' stands for "Change lines"
+                // exactly one line replaced by one line
+                &mut output,
+                "{line_number_expected}c{line_number_actual}"
+            )
+            .unwrap(),
+            (1, _) => writeln!(
+                // one line replaced by multiple lines
+                &mut output,
+                "{}c{},{}",
+                line_number_expected,
+                line_number_actual,
+                actual_count + line_number_actual - 1
+            )
+            .unwrap(),
+            (_, 1) => writeln!(
+                // multiple lines replaced by one line
+                &mut output,
+                "{},{}c{}",
+                line_number_expected,
+                expected_count + line_number_expected - 1,
+                line_number_actual
+            )
+            .unwrap(),
+            _ => writeln!(
+                // general case: multiple lines replaced by multiple lines
+                &mut output,
+                "{},{}c{},{}",
+                line_number_expected,
+                expected_count + line_number_expected - 1,
+                line_number_actual,
+                actual_count + line_number_actual - 1
+            )
+            .unwrap(),
+        }
+        for expected in &result.expected {
+            write!(&mut output, "< ").unwrap();
+            do_write_line(&mut output, expected, params.expand_tabs, params.tabsize).unwrap();
+            writeln!(&mut output).unwrap();
+        }
+        if result.expected_missing_nl {
+            writeln!(&mut output, r"\ No newline at end of file").unwrap();
+        }
+        if expected_count != 0 && actual_count != 0 {
+            writeln!(&mut output, "---").unwrap();
+        }
+        for actual in &result.actual {
+            write!(&mut output, "> ").unwrap();
+            do_write_line(&mut output, actual, params.expand_tabs, params.tabsize).unwrap();
+            writeln!(&mut output).unwrap();
+        }
+        if result.actual_missing_nl {
+            writeln!(&mut output, r"\ No newline at end of file").unwrap();
+        }
+    }
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    use crate::utils::testcmds::PATCH_CMD;
+
+    #[test]
+    fn test_basic() {
+        let mut a = Vec::new();
+        a.write_all(b"a\n").unwrap();
+        let mut b = Vec::new();
+        b.write_all(b"b\n").unwrap();
+        let diff = diff(&a, &b, &Params::default());
+        let expected = b"1c1\n< a\n---\n> b\n".to_vec();
+        assert_eq!(diff, expected);
+    }
+
+    #[test]
+    fn test_permutations() {
+        let target = "target/normal-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"b\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"e\n" } else { b"f\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"g\n" } else { b"h\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"i\n" } else { b"j\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"k\n" } else { b"l\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff(&alef, &bet, &Params::default());
+                                File::create(format!("{target}/ab.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg(format!("{target}/alef"))
+                                    .stdin(File::open(format!("{target}/ab.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alef")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_missing_line_ending() {
+        let target = "target/normal-diff/";
+        // test all possible six-line files with missing newlines.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                for &g in &[0, 1, 2] {
+                                    use std::fs::{self, File};
+                                    use std::io::Write;
+                                    let mut alef = Vec::new();
+                                    let mut bet = Vec::new();
+                                    alef.write_all(if a == 0 { b"a\n" } else { b"b\n" })
+                                        .unwrap();
+                                    if a != 2 {
+                                        bet.write_all(b"b\n").unwrap();
+                                    }
+                                    alef.write_all(if b == 0 { b"c\n" } else { b"d\n" })
+                                        .unwrap();
+                                    if b != 2 {
+                                        bet.write_all(b"d\n").unwrap();
+                                    }
+                                    alef.write_all(if c == 0 { b"e\n" } else { b"f\n" })
+                                        .unwrap();
+                                    if c != 2 {
+                                        bet.write_all(b"f\n").unwrap();
+                                    }
+                                    alef.write_all(if d == 0 { b"g\n" } else { b"h\n" })
+                                        .unwrap();
+                                    if d != 2 {
+                                        bet.write_all(b"h\n").unwrap();
+                                    }
+                                    alef.write_all(if e == 0 { b"i\n" } else { b"j\n" })
+                                        .unwrap();
+                                    if e != 2 {
+                                        bet.write_all(b"j\n").unwrap();
+                                    }
+                                    alef.write_all(if f == 0 { b"k\n" } else { b"l\n" })
+                                        .unwrap();
+                                    if f != 2 {
+                                        bet.write_all(b"l\n").unwrap();
+                                    }
+                                    match g {
+                                        0 => {
+                                            alef.pop();
+                                        }
+                                        1 => {
+                                            bet.pop();
+                                        }
+                                        2 => {
+                                            alef.pop();
+                                            bet.pop();
+                                        }
+                                        _ => unreachable!(),
+                                    }
+                                    // This test diff is intentionally reversed.
+                                    // We want it to turn the alef into bet.
+                                    let diff = diff(&alef, &bet, &Params::default());
+                                    File::create(format!("{target}/abn.diff"))
+                                        .unwrap()
+                                        .write_all(&diff)
+                                        .unwrap();
+                                    let mut fa = File::create(format!("{target}/alefn")).unwrap();
+                                    fa.write_all(&alef[..]).unwrap();
+                                    let mut fb = File::create(format!("{target}/betn")).unwrap();
+                                    fb.write_all(&bet[..]).unwrap();
+                                    let _ = fa;
+                                    let _ = fb;
+                                    let output = PATCH_CMD
+                                        .new()
+                                        .arg("-p0")
+                                        .arg("--normal")
+                                        .arg(format!("{target}/alefn"))
+                                        .stdin(File::open(format!("{target}/abn.diff")).unwrap())
+                                        .output()
+                                        .unwrap();
+                                    assert!(output.status.success(), "{output:?}");
+                                    //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                    //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                    let alef = fs::read(format!("{target}/alefn")).unwrap();
+                                    assert_eq!(alef, bet);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_empty_lines() {
+        let target = "target/normal-diff/";
+        // test all possible six-line files with missing newlines.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"\n" } else { b"b\n" }).unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"\n" } else { b"d\n" }).unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"\n" } else { b"f\n" }).unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"\n" } else { b"h\n" }).unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"h\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"\n" } else { b"j\n" }).unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"j\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"\n" } else { b"l\n" }).unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"l\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff(&alef, &bet, &Params::default());
+                                File::create(format!("{target}/ab_.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alef_")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/bet_")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg(format!("{target}/alef_"))
+                                    .stdin(File::open(format!("{target}/ab_.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alef_")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_permutations_reverse() {
+        let target = "target/normal-diff/";
+        // test all possible six-line files.
+        let _ = std::fs::create_dir(target);
+        for &a in &[0, 1, 2] {
+            for &b in &[0, 1, 2] {
+                for &c in &[0, 1, 2] {
+                    for &d in &[0, 1, 2] {
+                        for &e in &[0, 1, 2] {
+                            for &f in &[0, 1, 2] {
+                                use std::fs::{self, File};
+                                use std::io::Write;
+                                let mut alef = Vec::new();
+                                let mut bet = Vec::new();
+                                alef.write_all(if a == 0 { b"a\n" } else { b"f\n" })
+                                    .unwrap();
+                                if a != 2 {
+                                    bet.write_all(b"a\n").unwrap();
+                                }
+                                alef.write_all(if b == 0 { b"b\n" } else { b"e\n" })
+                                    .unwrap();
+                                if b != 2 {
+                                    bet.write_all(b"b\n").unwrap();
+                                }
+                                alef.write_all(if c == 0 { b"c\n" } else { b"d\n" })
+                                    .unwrap();
+                                if c != 2 {
+                                    bet.write_all(b"c\n").unwrap();
+                                }
+                                alef.write_all(if d == 0 { b"d\n" } else { b"c\n" })
+                                    .unwrap();
+                                if d != 2 {
+                                    bet.write_all(b"d\n").unwrap();
+                                }
+                                alef.write_all(if e == 0 { b"e\n" } else { b"b\n" })
+                                    .unwrap();
+                                if e != 2 {
+                                    bet.write_all(b"e\n").unwrap();
+                                }
+                                alef.write_all(if f == 0 { b"f\n" } else { b"a\n" })
+                                    .unwrap();
+                                if f != 2 {
+                                    bet.write_all(b"f\n").unwrap();
+                                }
+                                // This test diff is intentionally reversed.
+                                // We want it to turn the alef into bet.
+                                let diff = diff(&alef, &bet, &Params::default());
+                                File::create(format!("{target}/abr.diff"))
+                                    .unwrap()
+                                    .write_all(&diff)
+                                    .unwrap();
+                                let mut fa = File::create(format!("{target}/alefr")).unwrap();
+                                fa.write_all(&alef[..]).unwrap();
+                                let mut fb = File::create(format!("{target}/betr")).unwrap();
+                                fb.write_all(&bet[..]).unwrap();
+                                let _ = fa;
+                                let _ = fb;
+                                let output = PATCH_CMD
+                                    .new()
+                                    .arg("-p0")
+                                    .arg(format!("{target}/alefr"))
+                                    .stdin(File::open(format!("{target}/abr.diff")).unwrap())
+                                    .output()
+                                    .unwrap();
+                                assert!(output.status.success(), "{output:?}");
+                                //println!("{}", String::from_utf8_lossy(&output.stdout));
+                                //println!("{}", String::from_utf8_lossy(&output.stderr));
+                                let alef = fs::read(format!("{target}/alefr")).unwrap();
+                                assert_eq!(alef, bet);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_stop_early() {
+        let from = ["a", "b", "c"].join("\n");
+        let to = ["a", "d", "c"].join("\n");
+
+        let diff_full = diff(from.as_bytes(), to.as_bytes(), &Params::default());
+        let expected_full = ["2c2", "< b", "---", "> d", ""].join("\n");
+        assert_eq!(diff_full, expected_full.as_bytes());
+
+        let diff_brief = diff(
+            from.as_bytes(),
+            to.as_bytes(),
+            &Params {
+                brief: true,
+                ..Default::default()
+            },
+        );
+        let expected_brief = "\0".as_bytes();
+        assert_eq!(diff_brief, expected_brief);
+
+        let nodiff_full = diff(from.as_bytes(), from.as_bytes(), &Params::default());
+        assert!(nodiff_full.is_empty());
+
+        let nodiff_brief = diff(
+            from.as_bytes(),
+            from.as_bytes(),
+            &Params {
+                brief: true,
+                ..Default::default()
+            },
+        );
+        assert!(nodiff_brief.is_empty());
+    }
+}
@@ -0,0 +1,975 @@
+use std::ffi::OsString;
+use std::iter::Peekable;
+use std::path::PathBuf;
+
+use regex::Regex;
+
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub enum Format {
+    #[default]
+    Normal,
+    Unified,
+    Context,
+    Ed,
+    SideBySide,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Params {
+    pub executable: OsString,
+    pub from: OsString,
+    pub to: OsString,
+    pub format: Format,
+    pub context_count: usize,
+    pub report_identical_files: bool,
+    pub brief: bool,
+    pub recursive: bool,
+    pub expand_tabs: bool,
+    pub tabsize: usize,
+    pub width: usize,
+}
+
+impl Default for Params {
+    fn default() -> Self {
+        Self {
+            executable: OsString::default(),
+            from: OsString::default(),
+            to: OsString::default(),
+            format: Format::default(),
+            context_count: 3,
+            report_identical_files: false,
+            brief: false,
+            recursive: false,
+            expand_tabs: false,
+            tabsize: 8,
+            width: 130,
+        }
+    }
+}
+
+pub fn parse_params<I: Iterator<Item = OsString>>(mut opts: Peekable<I>) -> Result<Params, String> {
+    // parse CLI
+
+    let Some(executable) = opts.next() else {
+        return Err("Usage: <exe> <from> <to>".to_string());
+    };
+    let mut params = Params {
+        executable,
+        ..Default::default()
+    };
+    let mut from = None;
+    let mut to = None;
+    let mut format = None;
+    let mut context = None;
+    let tabsize_re = Regex::new(r"^--tabsize=(?<num>\d+)$").unwrap();
+    let width_re = Regex::new(r"^--width=(?P<long>\d+)$").unwrap();
+    while let Some(param) = opts.next() {
+        let next_param = opts.peek();
+        if param == "--" {
+            break;
+        }
+        if param == "-" {
+            if from.is_none() {
+                from = Some(param);
+            } else if to.is_none() {
+                to = Some(param);
+            } else {
+                return Err(format!(
+                    "Usage: {} <from> <to>",
+                    params.executable.to_string_lossy()
+                ));
+            }
+            continue;
+        }
+        if param == "-r" || param == "--recursive" {
+            params.recursive = true;
+            continue;
+        }
+        if param == "-s" || param == "--report-identical-files" {
+            params.report_identical_files = true;
+            continue;
+        }
+        if param == "-q" || param == "--brief" {
+            params.brief = true;
+            continue;
+        }
+        if param == "-t" || param == "--expand-tabs" {
+            params.expand_tabs = true;
+            continue;
+        }
+        if param == "--normal" {
+            if format.is_some() && format != Some(Format::Normal) {
+                return Err("Conflicting output style options".to_string());
+            }
+            format = Some(Format::Normal);
+            continue;
+        }
+        if param == "-e" || param == "--ed" {
+            if format.is_some() && format != Some(Format::Ed) {
+                return Err("Conflicting output style options".to_string());
+            }
+            format = Some(Format::Ed);
+            continue;
+        }
+        if param == "-y" || param == "--side-by-side" {
+            if format.is_some() && format != Some(Format::SideBySide) {
+                return Err("Conflicting output style option".to_string());
+            }
+            format = Some(Format::SideBySide);
+            continue;
+        }
+        if width_re.is_match(param.to_string_lossy().as_ref()) {
+            let param = param.into_string().unwrap();
+            let width_str: &str = width_re
+                .captures(param.as_str())
+                .unwrap()
+                .name("long")
+                .unwrap()
+                .as_str();
+
+            params.width = match width_str.parse::<usize>() {
+                Ok(num) => {
+                    if num == 0 {
+                        return Err("invalid width «0»".to_string());
+                    }
+
+                    num
+                }
+                Err(_) => return Err(format!("invalid width «{width_str}»")),
+            };
+            continue;
+        }
+        if tabsize_re.is_match(param.to_string_lossy().as_ref()) {
+            // Because param matches the regular expression,
+            // it is safe to assume it is valid UTF-8.
+            let param = param.into_string().unwrap();
+            let tabsize_str = tabsize_re
+                .captures(param.as_str())
+                .unwrap()
+                .name("num")
+                .unwrap()
+                .as_str();
+            params.tabsize = match tabsize_str.parse::<usize>() {
+                Ok(num) => {
+                    if num == 0 {
+                        return Err("invalid tabsize «0»".to_string());
+                    }
+
+                    num
+                }
+                Err(_) => return Err(format!("invalid tabsize «{tabsize_str}»")),
+            };
+
+            continue;
+        }
+        match match_context_diff_params(&param, next_param, format) {
+            Ok(DiffStyleMatch {
+                is_match,
+                context_count,
+                next_param_consumed,
+            }) => {
+                if is_match {
+                    format = Some(Format::Context);
+                    if context_count.is_some() {
+                        context = context_count;
+                    }
+                    if next_param_consumed {
+                        opts.next();
+                    }
+                    continue;
+                }
+            }
+            Err(error) => return Err(error),
+        }
+        match match_unified_diff_params(&param, next_param, format) {
+            Ok(DiffStyleMatch {
+                is_match,
+                context_count,
+                next_param_consumed,
+            }) => {
+                if is_match {
+                    format = Some(Format::Unified);
+                    if context_count.is_some() {
+                        context = context_count;
+                    }
+                    if next_param_consumed {
+                        opts.next();
+                    }
+                    continue;
+                }
+            }
+            Err(error) => return Err(error),
+        }
+        if param.to_string_lossy().starts_with('-') {
+            return Err(format!("unrecognized option '{}'", param.to_string_lossy()));
+        }
+        if from.is_none() {
+            from = Some(param);
+        } else if to.is_none() {
+            to = Some(param);
+        } else {
+            return Err(format!(
+                "Usage: {} <from> <to>",
+                params.executable.to_string_lossy()
+            ));
+        }
+    }
+    params.from = if let Some(from) = from {
+        from
+    } else if let Some(param) = opts.next() {
+        param
+    } else {
+        return Err(format!(
+            "Usage: {} <from> <to>",
+            params.executable.to_string_lossy()
+        ));
+    };
+    params.to = if let Some(to) = to {
+        to
+    } else if let Some(param) = opts.next() {
+        param
+    } else {
+        return Err(format!(
+            "Usage: {} <from> <to>",
+            params.executable.to_string_lossy()
+        ));
+    };
+
+    // diff DIRECTORY FILE => diff DIRECTORY/FILE FILE
+    // diff FILE DIRECTORY => diff FILE DIRECTORY/FILE
+    let mut from_path: PathBuf = PathBuf::from(&params.from);
+    let mut to_path: PathBuf = PathBuf::from(&params.to);
+
+    if from_path.is_dir() && to_path.is_file() {
+        from_path.push(to_path.file_name().unwrap());
+        params.from = from_path.into_os_string();
+    } else if from_path.is_file() && to_path.is_dir() {
+        to_path.push(from_path.file_name().unwrap());
+        params.to = to_path.into_os_string();
+    }
+
+    params.format = format.unwrap_or(Format::default());
+    if let Some(context_count) = context {
+        params.context_count = context_count;
+    }
+    Ok(params)
+}
+
+struct DiffStyleMatch {
+    is_match: bool,
+    context_count: Option<usize>,
+    next_param_consumed: bool,
+}
+
+fn match_context_diff_params(
+    param: &OsString,
+    next_param: Option<&OsString>,
+    format: Option<Format>,
+) -> Result<DiffStyleMatch, String> {
+    const CONTEXT_RE: &str = r"^(-[cC](?<num1>\d*)|--context(=(?<num2>\d*))?|-(?<num3>\d+)c)$";
+    let regex = Regex::new(CONTEXT_RE).unwrap();
+    let is_match = regex.is_match(param.to_string_lossy().as_ref());
+    let mut context_count = None;
+    let mut next_param_consumed = false;
+    if is_match {
+        if format.is_some() && format != Some(Format::Context) {
+            return Err("Conflicting output style options".to_string());
+        }
+        let captures = regex.captures(param.to_str().unwrap()).unwrap();
+        let num = captures
+            .name("num1")
+            .or(captures.name("num2"))
+            .or(captures.name("num3"));
+        if let Some(numvalue) = num {
+            if !numvalue.as_str().is_empty() {
+                context_count = Some(numvalue.as_str().parse::<usize>().unwrap());
+            }
+        }
+        if param == "-C" {
+            if let Some(p) = next_param {
+                let size_str = p.to_string_lossy();
+                match size_str.parse::<usize>() {
+                    Ok(context_size) => {
+                        context_count = Some(context_size);
+                        next_param_consumed = true;
+                    }
+                    Err(_) => return Err(format!("invalid context length '{size_str}'")),
+                }
+            }
+        }
+    }
+    Ok(DiffStyleMatch {
+        is_match,
+        context_count,
+        next_param_consumed,
+    })
+}
+
+fn match_unified_diff_params(
+    param: &OsString,
+    next_param: Option<&OsString>,
+    format: Option<Format>,
+) -> Result<DiffStyleMatch, String> {
+    const UNIFIED_RE: &str = r"^(-[uU](?<num1>\d*)|--unified(=(?<num2>\d*))?|-(?<num3>\d+)u)$";
+    let regex = Regex::new(UNIFIED_RE).unwrap();
+    let is_match = regex.is_match(param.to_string_lossy().as_ref());
+    let mut context_count = None;
+    let mut next_param_consumed = false;
+    if is_match {
+        if format.is_some() && format != Some(Format::Unified) {
+            return Err("Conflicting output style options".to_string());
+        }
+        let captures = regex.captures(param.to_str().unwrap()).unwrap();
+        let num = captures
+            .name("num1")
+            .or(captures.name("num2"))
+            .or(captures.name("num3"));
+        if let Some(numvalue) = num {
+            if !numvalue.as_str().is_empty() {
+                context_count = Some(numvalue.as_str().parse::<usize>().unwrap());
+            }
+        }
+        if param == "-U" {
+            if let Some(p) = next_param {
+                let size_str = p.to_string_lossy();
+                match size_str.parse::<usize>() {
+                    Ok(context_size) => {
+                        context_count = Some(context_size);
+                        next_param_consumed = true;
+                    }
+                    Err(_) => return Err(format!("invalid context length '{size_str}'")),
+                }
+            }
+        }
+    }
+    Ok(DiffStyleMatch {
+        is_match,
+        context_count,
+        next_param_consumed,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    fn os(s: &str) -> OsString {
+        OsString::from(s)
+    }
+    #[test]
+    fn basics() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--normal"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[test]
+    fn basics_ed() {
+        for arg in ["-e", "--ed"] {
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    format: Format::Ed,
+                    ..Default::default()
+                }),
+                parse_params(
+                    [os("diff"), os(arg), os("foo"), os("bar")]
+                        .iter()
+                        .cloned()
+                        .peekable()
+                )
+            );
+        }
+    }
+    #[test]
+    fn context_valid() {
+        for args in [vec!["-c"], vec!["--context"], vec!["--context="]] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    format: Format::Context,
+                    ..Default::default()
+                }),
+                parse_params(params.iter().map(|x| os(x)).peekable())
+            );
+        }
+        for args in [
+            vec!["-c42"],
+            vec!["-C42"],
+            vec!["-C", "42"],
+            vec!["--context=42"],
+            vec!["-42c"],
+        ] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    format: Format::Context,
+                    context_count: 42,
+                    ..Default::default()
+                }),
+                parse_params(params.iter().map(|x| os(x)).peekable())
+            );
+        }
+    }
+    #[test]
+    fn context_invalid() {
+        for args in [
+            vec!["-c", "42"],
+            vec!["-c=42"],
+            vec!["-c="],
+            vec!["-C"],
+            vec!["-C=42"],
+            vec!["-C="],
+            vec!["--context42"],
+            vec!["--context", "42"],
+            vec!["-42C"],
+        ] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert!(parse_params(params.iter().map(|x| os(x)).peekable()).is_err());
+        }
+    }
+    #[test]
+    fn unified_valid() {
+        for args in [vec!["-u"], vec!["--unified"], vec!["--unified="]] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    format: Format::Unified,
+                    ..Default::default()
+                }),
+                parse_params(params.iter().map(|x| os(x)).peekable())
+            );
+        }
+        for args in [
+            vec!["-u42"],
+            vec!["-U42"],
+            vec!["-U", "42"],
+            vec!["--unified=42"],
+            vec!["-42u"],
+        ] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    format: Format::Unified,
+                    context_count: 42,
+                    ..Default::default()
+                }),
+                parse_params(params.iter().map(|x| os(x)).peekable())
+            );
+        }
+    }
+    #[test]
+    fn unified_invalid() {
+        for args in [
+            vec!["-u", "42"],
+            vec!["-u=42"],
+            vec!["-u="],
+            vec!["-U"],
+            vec!["-U=42"],
+            vec!["-U="],
+            vec!["--unified42"],
+            vec!["--unified", "42"],
+            vec!["-42U"],
+        ] {
+            let mut params = vec!["diff"];
+            params.extend(args);
+            params.extend(["foo", "bar"]);
+            assert!(parse_params(params.iter().map(|x| os(x)).peekable()).is_err());
+        }
+    }
+    #[test]
+    fn context_count() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                format: Format::Unified,
+                context_count: 54,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-u54"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                format: Format::Unified,
+                context_count: 54,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-U54"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                format: Format::Unified,
+                context_count: 54,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-U"), os("54"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                format: Format::Context,
+                context_count: 54,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-c54"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[test]
+    fn report_identical_files() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                report_identical_files: true,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-s"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                report_identical_files: true,
+                ..Default::default()
+            }),
+            parse_params(
+                [
+                    os("diff"),
+                    os("--report-identical-files"),
+                    os("foo"),
+                    os("bar"),
+                ]
+                .iter()
+                .cloned()
+                .peekable()
+            )
+        );
+    }
+    #[test]
+    fn brief() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                brief: true,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("-q"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                brief: true,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--brief"), os("foo"), os("bar"),]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[test]
+    fn expand_tabs() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        for option in ["-t", "--expand-tabs"] {
+            assert_eq!(
+                Ok(Params {
+                    executable: os("diff"),
+                    from: os("foo"),
+                    to: os("bar"),
+                    expand_tabs: true,
+                    ..Default::default()
+                }),
+                parse_params(
+                    [os("diff"), os(option), os("foo"), os("bar")]
+                        .iter()
+                        .cloned()
+                        .peekable()
+                )
+            );
+        }
+    }
+    #[test]
+    fn tabsize() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                tabsize: 1,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--tabsize=1"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                tabsize: 42,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--tabsize=42"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+        assert!(parse_params(
+            [os("diff"), os("--tabsize"), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [os("diff"), os("--tabsize="), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [os("diff"), os("--tabsize=r2"), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [os("diff"), os("--tabsize=-1"), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [os("diff"), os("--tabsize=r2"), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [
+                os("diff"),
+                os("--tabsize=92233720368547758088"),
+                os("foo"),
+                os("bar")
+            ]
+            .iter()
+            .cloned()
+            .peekable()
+        )
+        .is_err());
+    }
+    #[test]
+    fn width() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("bar"),
+                width: 100,
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--width=100"), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[test]
+    fn width_suffix_is_an_operand() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("xyz--width=5"),
+                to: os("foo"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("xyz--width=5"), os("foo")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[cfg(unix)]
+    #[test]
+    fn width_non_utf8_is_not_an_option() {
+        use std::os::unix::ffi::OsStringExt;
+        // used to panic in into_string().unwrap()
+        let bad = OsString::from_vec(b"\xff--width=5".to_vec());
+        let params = parse_params(
+            [os("diff"), bad.clone(), os("foo")]
+                .iter()
+                .cloned()
+                .peekable(),
+        )
+        .unwrap();
+        assert_eq!(params.from, bad);
+    }
+    #[test]
+    fn double_dash() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("-g"),
+                to: os("-h"),
+                ..Default::default()
+            }),
+            parse_params(
+                [os("diff"), os("--"), os("-g"), os("-h")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+        );
+    }
+    #[test]
+    fn default_to_stdin() {
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("foo"),
+                to: os("-"),
+                ..Default::default()
+            }),
+            parse_params([os("diff"), os("foo"), os("-")].iter().cloned().peekable())
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("-"),
+                to: os("bar"),
+                ..Default::default()
+            }),
+            parse_params([os("diff"), os("-"), os("bar")].iter().cloned().peekable())
+        );
+        assert_eq!(
+            Ok(Params {
+                executable: os("diff"),
+                from: os("-"),
+                to: os("-"),
+                ..Default::default()
+            }),
+            parse_params([os("diff"), os("-"), os("-")].iter().cloned().peekable())
+        );
+        assert!(parse_params(
+            [os("diff"), os("foo"), os("bar"), os("-")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(parse_params(
+            [os("diff"), os("-"), os("-"), os("-")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+    }
+    #[test]
+    fn missing_arguments() {
+        assert!(parse_params([os("diff")].iter().cloned().peekable()).is_err());
+        assert!(parse_params([os("diff"), os("foo")].iter().cloned().peekable()).is_err());
+    }
+    #[test]
+    fn unknown_argument() {
+        assert!(parse_params(
+            [os("diff"), os("-g"), os("foo"), os("bar")]
+                .iter()
+                .cloned()
+                .peekable()
+        )
+        .is_err());
+        assert!(
+            parse_params([os("diff"), os("-g"), os("bar")].iter().cloned().peekable()).is_err()
+        );
+        assert!(parse_params([os("diff"), os("-g")].iter().cloned().peekable()).is_err());
+    }
+    #[test]
+    fn empty() {
+        assert!(parse_params([].iter().cloned().peekable()).is_err());
+    }
+    #[test]
+    fn conflicting_output_styles() {
+        for (arg1, arg2) in [
+            ("-u", "-c"),
+            ("-u", "-e"),
+            ("-c", "-u"),
+            ("-c", "-U42"),
+            ("-u", "--normal"),
+            ("--normal", "-e"),
+            ("--context", "--normal"),
+        ] {
+            assert!(parse_params(
+                [os("diff"), os(arg1), os(arg2), os("foo"), os("bar")]
+                    .iter()
+                    .cloned()
+                    .peekable()
+            )
+            .is_err());
+        }
+    }
+}
@@ -0,0 +1,300 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use regex::Regex;
+use std::{ffi::OsString, io::Write};
+use unicode_width::UnicodeWidthStr;
+
+/// Replace tabs by spaces in the input line.
+/// Correctly handle multi-bytes characters.
+/// This assumes that line does not contain any line breaks (if it does, the result is undefined).
+#[must_use]
+pub fn do_expand_tabs(line: &[u8], tabsize: usize) -> Vec<u8> {
+    let tab = b'\t';
+    let ntabs = line.iter().filter(|c| **c == tab).count();
+    if ntabs == 0 {
+        return line.to_vec();
+    }
+    let mut result = Vec::with_capacity(line.len() + ntabs * (tabsize - 1));
+    let mut offset = 0;
+
+    let mut iter = line.split(|c| *c == tab).peekable();
+    while let Some(chunk) = iter.next() {
+        match String::from_utf8(chunk.to_vec()) {
+            Ok(s) => offset += UnicodeWidthStr::width(s.as_str()),
+            Err(_) => offset += chunk.len(),
+        }
+        result.extend_from_slice(chunk);
+        if iter.peek().is_some() {
+            result.resize(result.len() + tabsize - offset % tabsize, b' ');
+            offset = 0;
+        }
+    }
+
+    result
+}
+
+/// Write a single line to an output stream, expanding tabs to space if necessary.
+/// This assumes that line does not contain any line breaks
+/// (if it does and tabs are to be expanded to spaces, the result is undefined).
+pub fn do_write_line(
+    output: &mut Vec<u8>,
+    line: &[u8],
+    expand_tabs: bool,
+    tabsize: usize,
+) -> std::io::Result<()> {
+    if expand_tabs {
+        output.write_all(do_expand_tabs(line, tabsize).as_slice())
+    } else {
+        output.write_all(line)
+    }
+}
+
+/// Retrieves the modification time of the input file specified by file path
+/// If an error occurs, it returns the current system time
+pub fn get_modification_time(file_path: &str) -> String {
+    use chrono::{DateTime, Local};
+    use std::fs;
+    use std::time::SystemTime;
+
+    let modification_time: SystemTime = fs::metadata(file_path)
+        .and_then(|m| m.modified())
+        .unwrap_or(SystemTime::now());
+
+    let modification_time: DateTime<Local> = modification_time.into();
+    let modification_time: String = modification_time
+        .format("%Y-%m-%d %H:%M:%S%.9f %z")
+        .to_string();
+
+    modification_time
+}
+
+pub fn format_failure_to_read_input_file(
+    executable: &OsString,
+    filepath: &OsString,
+    error: &std::io::Error,
+) -> String {
+    // std::io::Error's display trait outputs "{detail} (os error {code})"
+    // but we want only the {detail} (error string) part
+    let error_code_re = Regex::new(r"\ \(os\ error\ \d+\)$").unwrap();
+    format!(
+        "{}: {}: {}",
+        executable.to_string_lossy(),
+        filepath.to_string_lossy(),
+        error_code_re.replace(error.to_string().as_str(), ""),
+    )
+}
+
+pub fn report_failure_to_read_input_file(
+    executable: &OsString,
+    filepath: &OsString,
+    error: &std::io::Error,
+) {
+    eprintln!(
+        "{}",
+        format_failure_to_read_input_file(executable, filepath, error)
+    );
+}
+
+#[cfg(test)]
+pub mod testcmds {
+    // Command construction wrapper that provides some validation and non-obscure, "fail fast"
+    // feedback and error messages.
+    use std::any::Any;
+    use std::io::Write;
+    use std::panic::catch_unwind;
+    use std::process::{Command, Stdio};
+    use std::sync::LazyLock;
+
+    pub struct CmdFactory {
+        cmd: &'static str,
+        validated_once: LazyLock<Result<(), String>>,
+        validate: fn(&CmdFactory) -> (),
+    }
+
+    impl CmdFactory {
+        pub fn new(&self) -> Command {
+            match &*self.validated_once {
+                Ok(()) => Command::new(self.cmd),
+                Err(errmsg) => panic!(
+                    "'{}' validation failed in earlier thread/test: {}",
+                    self.cmd, errmsg
+                ),
+            }
+        }
+        // "self" is not compatible with static initialization
+        fn try_catch_validate(cmd: &CmdFactory) -> Result<(), String> {
+            // Note catch_unwind() does _not_ hide error messages, stack traces, etc.
+            catch_unwind(|| {
+                let _ = (cmd.validate)(cmd);
+            })
+            .map_err(find_panic_message)
+        }
+    }
+
+    fn find_panic_message(payload: Box<dyn Any + Send>) -> String {
+        // https://github.com/rust-lang/rust/blob/1.95.0/library/std/src/panicking.rs#L771
+        if let Some(&s) = payload.downcast_ref::<&'static str>() {
+            String::from(s)
+        } else if let Some(s) = payload.downcast_ref::<String>() {
+            s.clone()
+        } else {
+            format!(
+                "Unusual panic payload type {:?}, look for the first thread/test that failed",
+                payload.type_id(),
+            )
+        }
+    }
+
+    pub static PATCH_CMD: CmdFactory = CmdFactory {
+        cmd: if cfg!(target_os = "macos") {
+            "gpatch" // brew install gpatch
+        } else {
+            "patch"
+        },
+        validated_once: LazyLock::new(|| CmdFactory::try_catch_validate(&PATCH_CMD)),
+
+        validate: (|myself| {
+            let output = Command::new(myself.cmd)
+                .arg("--version")
+                .output()
+                .expect(format!("`{} --version` failed", myself.cmd).as_str());
+            // Non-GNU versions have subtle differences. When some newlines are missing in some test
+            // patches, the macOS version can even stall the whole test run.
+            assert!(output.stdout.starts_with(b"GNU patch"));
+            assert!(output.status.success());
+        }),
+    };
+
+    pub static ED_CMD: CmdFactory = CmdFactory {
+        cmd: "ed",
+        validated_once: LazyLock::new(|| CmdFactory::try_catch_validate(&ED_CMD)),
+
+        validate: (|myself| {
+            let mut child = Command::new(myself.cmd)
+                .arg("!echo hello_ed")
+                .stdin(Stdio::piped())
+                .stdout(Stdio::piped())
+                .spawn()
+                .expect("Failed to start 'ed' command");
+
+            let mut stdin = child.stdin.take().unwrap();
+            writeln!(stdin, "1p\nq").expect("Failed to send command to 'ed'");
+
+            let output = child
+                .wait_with_output()
+                .expect("Failed to read 'ed' stdout");
+            assert_eq!(String::from_utf8_lossy(&output.stdout), "9\nhello_ed\n");
+        }),
+    };
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    mod expand_tabs {
+        use super::*;
+        use pretty_assertions::assert_eq;
+
+        fn assert_tab_expansion(line: &str, tabsize: usize, expected: &str) {
+            assert_eq!(
+                do_expand_tabs(line.as_bytes(), tabsize),
+                expected.as_bytes()
+            );
+        }
+
+        #[test]
+        fn basics() {
+            assert_tab_expansion("foo barr   baz", 8, "foo barr   baz");
+            assert_tab_expansion("foo\tbarr\tbaz", 8, "foo     barr    baz");
+            assert_tab_expansion("foo\tbarr\tbaz", 5, "foo  barr baz");
+            assert_tab_expansion("foo\tbarr\tbaz", 2, "foo barr  baz");
+        }
+
+        #[test]
+        fn multibyte_chars() {
+            assert_tab_expansion("foo\tépée\tbaz", 8, "foo     épée    baz");
+            assert_tab_expansion("foo\t😉\tbaz", 5, "foo  😉   baz");
+
+            // Note: The Woman Scientist emoji (👩‍🔬) is a ZWJ sequence combining
+            // the Woman emoji (👩) and the Microscope emoji (🔬). On supported platforms
+            // it is displayed as a single emoji and has a print size of 2 columns.
+            // Terminal emulators tend to not support this, and display the two emojis
+            // side by side, thus accounting for a print size of 4 columns, but the
+            // unicode_width crate reports a correct size of 2.
+            assert_tab_expansion("foo\t👩‍🔬\tbaz", 6, "foo   👩‍🔬    baz");
+        }
+
+        #[test]
+        fn invalid_utf8() {
+            // [240, 240, 152, 137] is an invalid UTF-8 sequence, so it is handled as 4 bytes
+            assert_eq!(
+                do_expand_tabs(&[240, 240, 152, 137, 9, 102, 111, 111], 8),
+                &[240, 240, 152, 137, 32, 32, 32, 32, 102, 111, 111]
+            );
+        }
+    }
+
+    mod write_line {
+        use super::*;
+        use pretty_assertions::assert_eq;
+
+        fn assert_line_written(line: &str, expand_tabs: bool, tabsize: usize, expected: &str) {
+            let mut output: Vec<u8> = Vec::new();
+            assert!(do_write_line(&mut output, line.as_bytes(), expand_tabs, tabsize).is_ok());
+            assert_eq!(output, expected.as_bytes());
+        }
+
+        #[test]
+        fn basics() {
+            assert_line_written("foo bar baz", false, 8, "foo bar baz");
+            assert_line_written("foo bar\tbaz", false, 8, "foo bar\tbaz");
+            assert_line_written("foo bar\tbaz", true, 8, "foo bar baz");
+        }
+    }
+
+    mod modification_time {
+        use super::*;
+
+        #[test]
+        fn set_time() {
+            use chrono::{DateTime, Local};
+            use std::time::SystemTime;
+            use tempfile::NamedTempFile;
+
+            let temp = NamedTempFile::new().unwrap();
+            // set file modification time equal to current time
+            let current = SystemTime::now();
+            let _ = temp.as_file().set_modified(current);
+
+            // format current time
+            let current: DateTime<Local> = current.into();
+            let current: String = current.format("%Y-%m-%d %H:%M:%S%.9f %z").to_string();
+
+            // verify
+            assert_eq!(
+                current,
+                get_modification_time(&temp.path().to_string_lossy())
+            );
+        }
+
+        #[test]
+        fn invalid_file() {
+            use chrono::{DateTime, Local};
+            use std::time::SystemTime;
+
+            let invalid_file = "target/utils/invalid-file";
+
+            // store current time before calling `get_modification_time`
+            // Because the file is invalid, it will return SystemTime::now()
+            // which will be greater than previously saved time
+            let current_time: DateTime<Local> = SystemTime::now().into();
+            let m_time: DateTime<Local> = get_modification_time(invalid_file).parse().unwrap();
+
+            assert!(m_time > current_time);
+        }
+    }
+}
@@ -0,0 +1,945 @@
+// This file is part of the uutils diffutils package.
+//
+// For the full copyright and license information, please view the LICENSE-*
+// files that was distributed with this source code.
+
+use assert_cmd::cargo::cargo_bin_cmd;
+use predicates::prelude::*;
+use std::fs::File;
+#[cfg(not(windows))]
+use std::fs::OpenOptions;
+use std::io::Write;
+use tempfile::{tempdir, NamedTempFile};
+
+// Integration tests for the diffutils command
+mod common {
+    use super::*;
+
+    #[test]
+    fn unknown_param() -> Result<(), Box<dyn std::error::Error>> {
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("patch");
+        cmd.assert()
+            .code(predicate::eq(2))
+            .failure()
+            .stderr(predicate::eq("patch: utility not supported\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::starts_with(
+                "Expected utility name as second argument, got nothing.\n",
+            ));
+
+        for subcmd in ["diff", "cmp", "uu-diff", "uucmp"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg(subcmd);
+            cmd.arg("--foobar");
+            cmd.assert()
+                .code(predicate::eq(2))
+                .failure()
+                .stderr(predicate::str::contains("unrecognized option '--foobar'"));
+        }
+        Ok(())
+    }
+
+    #[test]
+    fn cannot_read_files() -> Result<(), Box<dyn std::error::Error>> {
+        let file = NamedTempFile::new()?;
+
+        let nofile = NamedTempFile::new()?;
+        let nopath = nofile.into_temp_path();
+        std::fs::remove_file(&nopath)?;
+
+        #[cfg(not(windows))]
+        let error_message = "No such file or directory";
+        #[cfg(windows)]
+        let error_message = "The system cannot find the file specified.";
+
+        for subcmd in ["diff", "cmp"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg(subcmd);
+            cmd.arg(&nopath).arg(file.path());
+            cmd.assert()
+                .code(predicate::eq(2))
+                .failure()
+                .stderr(predicate::str::ends_with(format!(
+                    ": {}: {error_message}\n",
+                    &nopath.as_os_str().to_string_lossy()
+                )));
+
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg(subcmd);
+            cmd.arg(file.path()).arg(&nopath);
+            cmd.assert()
+                .code(predicate::eq(2))
+                .failure()
+                .stderr(predicate::str::ends_with(format!(
+                    ": {}: {error_message}\n",
+                    &nopath.as_os_str().to_string_lossy()
+                )));
+        }
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg(&nopath).arg(&nopath);
+        cmd.assert().code(predicate::eq(2)).failure().stderr(
+            predicate::str::contains(format!(
+                ": {}: {error_message}\n",
+                &nopath.as_os_str().to_string_lossy()
+            ))
+            .count(2),
+        );
+
+        Ok(())
+    }
+}
+
+mod diff {
+    use diffutilslib::assert_diff_eq;
+
+    use super::*;
+
+    #[test]
+    fn no_differences() -> Result<(), Box<dyn std::error::Error>> {
+        let file = NamedTempFile::new()?;
+        for option in ["", "-u", "-c", "-e"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            if !option.is_empty() {
+                cmd.arg(option);
+            }
+            cmd.arg(file.path()).arg(file.path());
+            cmd.assert()
+                .code(predicate::eq(0))
+                .success()
+                .stdout(predicate::str::is_empty());
+        }
+        Ok(())
+    }
+
+    #[test]
+    fn no_differences_report_identical_files() -> Result<(), Box<dyn std::error::Error>> {
+        // same file
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("foo\n".as_bytes())?;
+        for option in ["", "-u", "-c", "-e"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            if !option.is_empty() {
+                cmd.arg(option);
+            }
+            cmd.arg("-s").arg(file1.path()).arg(file1.path());
+            cmd.assert()
+                .code(predicate::eq(0))
+                .success()
+                .stdout(predicate::eq(format!(
+                    "Files {} and {} are identical\n",
+                    file1.path().to_string_lossy(),
+                    file1.path().to_string_lossy(),
+                )));
+        }
+        // two files with the same content
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("foo\n".as_bytes())?;
+        for option in ["", "-u", "-c", "-e"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            if !option.is_empty() {
+                cmd.arg(option);
+            }
+            cmd.arg("-s").arg(file1.path()).arg(file2.path());
+            cmd.assert()
+                .code(predicate::eq(0))
+                .success()
+                .stdout(predicate::eq(format!(
+                    "Files {} and {} are identical\n",
+                    file1.path().to_string_lossy(),
+                    file2.path().to_string_lossy(),
+                )));
+        }
+        Ok(())
+    }
+
+    #[test]
+    fn differences() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("foo\n".as_bytes())?;
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("bar\n".as_bytes())?;
+        for option in ["", "-u", "-c", "-e"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            if !option.is_empty() {
+                cmd.arg(option);
+            }
+            cmd.arg(file1.path()).arg(file2.path());
+            cmd.assert()
+                .code(predicate::eq(1))
+                .failure()
+                .stdout(predicate::str::is_empty().not());
+        }
+        Ok(())
+    }
+
+    #[test]
+    fn differences_brief() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("foo\n".as_bytes())?;
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("bar\n".as_bytes())?;
+        for option in ["", "-u", "-c", "-e"] {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            if !option.is_empty() {
+                cmd.arg(option);
+            }
+            cmd.arg("-q").arg(file1.path()).arg(file2.path());
+            cmd.assert()
+                .code(predicate::eq(1))
+                .failure()
+                .stdout(predicate::eq(format!(
+                    "Files {} and {} differ\n",
+                    file1.path().to_string_lossy(),
+                    file2.path().to_string_lossy()
+                )));
+        }
+        Ok(())
+    }
+
+    #[test]
+    fn missing_newline() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("foo".as_bytes())?;
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("bar".as_bytes())?;
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-e").arg(file1.path()).arg(file2.path());
+        cmd.assert()
+            .code(predicate::eq(2))
+            .failure()
+            .stderr(predicate::str::starts_with("No newline at end of file"));
+        Ok(())
+    }
+
+    #[test]
+    fn read_from_stdin() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("foo\n".as_bytes())?;
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("bar\n".as_bytes())?;
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-u")
+            .arg(file1.path())
+            .arg("-")
+            .write_stdin("bar\n");
+        cmd.assert().code(predicate::eq(1)).failure();
+
+        let output = cmd.output().unwrap().stdout;
+        assert_diff_eq!(
+            output,
+            format!(
+                "--- {}\tTIMESTAMP\n+++ -\tTIMESTAMP\n@@ -1 +1 @@\n-foo\n+bar\n",
+                file1.path().to_string_lossy()
+            )
+        );
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-u")
+            .arg("-")
+            .arg(file2.path())
+            .write_stdin("foo\n");
+        cmd.assert().code(predicate::eq(1)).failure();
+
+        let output = cmd.output().unwrap().stdout;
+        assert_diff_eq!(
+            output,
+            format!(
+                "--- -\tTIMESTAMP\n+++ {}\tTIMESTAMP\n@@ -1 +1 @@\n-foo\n+bar\n",
+                file2.path().to_string_lossy()
+            )
+        );
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-u").arg("-").arg("-");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stdout(predicate::str::is_empty());
+
+        #[cfg(unix)]
+        {
+            let mut cmd = cargo_bin_cmd!("diffutils");
+            cmd.arg("diff");
+            cmd.arg("-u")
+                .arg(file1.path())
+                .arg("/dev/stdin")
+                .write_stdin("bar\n");
+            cmd.assert().code(predicate::eq(1)).failure();
+
+            let output = cmd.output().unwrap().stdout;
+            assert_diff_eq!(
+                output,
+                format!(
+                    "--- {}\tTIMESTAMP\n+++ /dev/stdin\tTIMESTAMP\n@@ -1 +1 @@\n-foo\n+bar\n",
+                    file1.path().to_string_lossy()
+                )
+            );
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn compare_file_to_directory() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let directory = tmp_dir.path().join("d");
+        let _ = std::fs::create_dir(&directory);
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"a\n").unwrap();
+
+        let da_path = directory.join("a");
+        let mut da = File::create(&da_path).unwrap();
+        da.write_all(b"da\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-u").arg(&directory).arg(&a_path);
+        cmd.assert().code(predicate::eq(1)).failure();
+
+        let output = cmd.output().unwrap().stdout;
+        assert_diff_eq!(
+            output,
+            format!(
+                "--- {}\tTIMESTAMP\n+++ {}\tTIMESTAMP\n@@ -1 +1 @@\n-da\n+a\n",
+                da_path.display(),
+                a_path.display()
+            )
+        );
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff");
+        cmd.arg("-u").arg(&a_path).arg(&directory);
+        cmd.assert().code(predicate::eq(1)).failure();
+
+        let output = cmd.output().unwrap().stdout;
+        assert_diff_eq!(
+            output,
+            format!(
+                "--- {}\tTIMESTAMP\n+++ {}\tTIMESTAMP\n@@ -1 +1 @@\n-a\n+da\n",
+                a_path.display(),
+                da_path.display()
+            )
+        );
+
+        Ok(())
+    }
+
+    // Regression for #269: the `-y` gutter marker must sit at the middle of the gutter.
+    #[test]
+    fn sdiff_gutter_marker_column() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file1 = NamedTempFile::new()?;
+        file1.write_all("aa\n".as_bytes())?;
+        let mut file2 = NamedTempFile::new()?;
+        file2.write_all("bb\n".as_bytes())?;
+
+        // --expand-tabs: padding is spaces.
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff")
+            .arg("-y")
+            .arg("--width=40")
+            .arg("--expand-tabs")
+            .arg(file1.path())
+            .arg(file2.path());
+        let output = cmd.output().unwrap().stdout;
+        assert_eq!(
+            output,
+            b"aa                 <\n                   >    bb\n"
+        );
+
+        // Default (expand_tabs: false): padding goes through the tab path.
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("diff")
+            .arg("-y")
+            .arg("--width=40")
+            .arg(file1.path())
+            .arg(file2.path());
+        let output = cmd.output().unwrap().stdout;
+        assert_eq!(output, b"aa\t\t   <\n\t\t   >\tbb\n");
+
+        Ok(())
+    }
+}
+
+mod cmp {
+    use super::*;
+
+    // A file whose metadata length is 0 but which still yields bytes (/dev/zero)
+    // collapses the offset column to two characters, so the padding subtraction
+    // underflowed once the running offset reached three digits.
+    #[test]
+    #[cfg(unix)]
+    fn cmp_verbose_zero_length_metadata() -> Result<(), Box<dyn std::error::Error>> {
+        let mut file = NamedTempFile::new()?;
+        file.write_all(&[0xffu8; 150])?;
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp")
+            .arg("--verbose")
+            .arg("/dev/zero")
+            .arg(file.path());
+        cmd.assert()
+            .code(predicate::eq(1))
+            .stdout(predicate::str::contains("150   0 377"));
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_incompatible_params() -> Result<(), Box<dyn std::error::Error>> {
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-s");
+        cmd.arg("/etc/passwd").arg("/etc/group");
+        cmd.assert()
+            .code(predicate::eq(2))
+            .failure()
+            .stderr(predicate::str::ends_with(
+                ": options -l and -s are incompatible\n",
+            ));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_stdin() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"a\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg(&a_path);
+        cmd.write_stdin("a\n");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg(&a_path);
+        cmd.write_stdin("b\n");
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(" - differ: char 1, line 1\n"));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_equal_files() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"a\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"a\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_one_file_empty() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"a\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let _ = File::create(&b_path).unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::contains(" EOF on "))
+            .stderr(predicate::str::ends_with(" which is empty\n"));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_immediate_difference() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"abc\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"bcd\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stdout(predicate::str::ends_with(" differ: char 1, line 1\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-b");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(
+                " differ: byte 1, line 1 is 141 a 142 b\n",
+            ));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::eq("1 141 142\n2 142 143\n3 143 144\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::eq(
+                "1 141 a    142 b\n2 142 b    143 c\n3 143 c    144 d\n",
+            ));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_newline_difference() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"abc\ndefg").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"abc\ndef\ng").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(" differ: char 8, line 2\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-b");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(
+                " differ: byte 8, line 2 is 147 g  12 ^J\n",
+            ));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stdout(predicate::str::starts_with("8 147  12\n"))
+            .stderr(predicate::str::contains(" EOF on"))
+            .stderr(predicate::str::ends_with(" after byte 8\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-b");
+        cmd.arg("-l");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stdout(predicate::str::starts_with("8 147 g     12 ^J\n"))
+            .stderr(predicate::str::contains(" EOF on"))
+            .stderr(predicate::str::ends_with(" after byte 8\n"));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_max_bytes() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"abc efg ijkl\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"abcdefghijkl\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg("-n");
+        cmd.arg("3");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg("-n");
+        cmd.arg("4");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::eq("4  40      144 d\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg("-n");
+        cmd.arg("13");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::eq(" 4  40      144 d\n 8  40      150 h\n"));
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_skip_args_parsing() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"---abc\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"###abc\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-i");
+        cmd.arg("3");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        // Positional skips should be ignored
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg("-i");
+        cmd.arg("3");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.arg("1").arg("1");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        // Single positional argument should only affect first file.
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.arg("3");
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(" differ: char 1, line 1\n"));
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.env("LC_ALL", "C");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.arg("3");
+        cmd.arg("3");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_skip_suffix_parsing() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        writeln!(a, "{}c", "a".repeat(1024)).unwrap();
+        a.flush().unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        writeln!(b, "{}c", "b".repeat(1024)).unwrap();
+        b.flush().unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("--ignore-initial=1K");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_skip() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(b"abc efg ijkl\n").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(b"abcdefghijkl\n").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg("-i");
+        cmd.arg("8");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::is_empty());
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-b");
+        cmd.arg("-i");
+        cmd.arg("4");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stderr(predicate::str::is_empty())
+            .stdout(predicate::str::ends_with(
+                " differ: byte 4, line 1 is  40   150 h\n",
+            ));
+
+        Ok(())
+    }
+
+    #[test]
+    fn cmp_binary() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        let mut bytes = vec![0, 15, 31, 32, 33, 40, 64, 126, 127, 128, 129, 200, 254, 255];
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(&bytes).unwrap();
+
+        bytes.reverse();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(&bytes).unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-l");
+        cmd.arg("-b");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stdout(predicate::eq(concat!(
+                " 1   0 ^@   377 M-^?\n",
+                " 2  17 ^O   376 M-~\n",
+                " 3  37 ^_   310 M-H\n",
+                " 4  40      201 M-^A\n",
+                " 5  41 !    200 M-^@\n",
+                " 6  50 (    177 ^?\n",
+                " 7 100 @    176 ~\n",
+                " 8 176 ~    100 @\n",
+                " 9 177 ^?    50 (\n",
+                "10 200 M-^@  41 !\n",
+                "11 201 M-^A  40  \n",
+                "12 310 M-H   37 ^_\n",
+                "13 376 M-~   17 ^O\n",
+                "14 377 M-^?   0 ^@\n"
+            )));
+
+        Ok(())
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn cmp_fast_paths() -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempdir()?;
+
+        // This test mimics one found in the GNU cmp test suite. It is used for
+        // validating the /dev/null optimization.
+        let a_path = tmp_dir.path().join("a");
+        let a = File::create(&a_path).unwrap();
+        a.set_len(14 * 1024 * 1024 * 1024 * 1024).unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let b = File::create(&b_path).unwrap();
+        b.set_len(15 * 1024 * 1024 * 1024 * 1024).unwrap();
+
+        let dev_null = OpenOptions::new().write(true).open("/dev/null").unwrap();
+
+        let mut child = std::process::Command::new(assert_cmd::cargo::cargo_bin!("diffutils"))
+            .arg("cmp")
+            .arg(&a_path)
+            .arg(&b_path)
+            .stdout(dev_null)
+            .spawn()
+            .unwrap();
+
+        // Bound the runtime to a very short time that still allows for some resource
+        // constraint to slow it down while also allowing very fast systems to exit as
+        // early as possible.
+        const MAX_TRIES: u8 = 50;
+        for tries in 0..=MAX_TRIES {
+            if tries == MAX_TRIES {
+                panic!("cmp took too long to run, /dev/null optimization probably not working")
+            }
+            match child.try_wait() {
+                Ok(Some(status)) => {
+                    assert_eq!(status.code(), Some(1));
+                    break;
+                }
+                Ok(None) => (),
+                Err(e) => panic!("{e:#?}"),
+            }
+            std::thread::sleep(std::time::Duration::from_millis(10));
+        }
+
+        // Two stdins should be equal
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg("-");
+        cmd.arg("-");
+        cmd.assert()
+            .code(predicate::eq(0))
+            .success()
+            .stdout(predicate::str::is_empty())
+            .stderr(predicate::str::is_empty());
+
+        // Files with longer than block size equal segments should still report
+        // the correct line number for the difference. Assumes 8KB block size (see
+        // https://github.com/rust-lang/rust/blob/master/library/std/src/sys_common/io.rs),
+        // create a 24KB equality.
+        let mut bytes = " ".repeat(4095);
+        bytes.push('\n');
+        bytes.push_str(&" ".repeat(4096));
+
+        let bytes = bytes.repeat(3);
+        let bytes = bytes.as_bytes();
+
+        let a_path = tmp_dir.path().join("a");
+        let mut a = File::create(&a_path).unwrap();
+        a.write_all(bytes).unwrap();
+        a.write_all(b"A").unwrap();
+
+        let b_path = tmp_dir.path().join("b");
+        let mut b = File::create(&b_path).unwrap();
+        b.write_all(bytes).unwrap();
+        b.write_all(b"B").unwrap();
+
+        let mut cmd = cargo_bin_cmd!("diffutils");
+        cmd.arg("cmp");
+        cmd.arg(&a_path).arg(&b_path);
+        cmd.env("LC_ALL", "en_US");
+        cmd.assert()
+            .code(predicate::eq(1))
+            .failure()
+            .stdout(predicate::str::ends_with(" differ: byte 24577, line 4\n"));
+
+        Ok(())
+    }
+}
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# Print the test results written to a JSON file by run-upstream-testsuite.sh
+# in a markdown format. The printout includes the name of the test, the result,
+# the URL to the test script and the contents of stdout and stderr.
+# It can be used verbatim as the description when filing an issue for a test
+# with an unexpected result.
+
+json="test-results.json"
+[[ -n $1 ]] && json="$1"
+
+codeblock () { echo -e "\`\`\`\n$1\n\`\`\`"; }
+
+jq -c '.tests[]' "$json" | while read -r test
+do
+  name=$(echo "$test" | jq -r '.test')
+  echo "# test: $name"
+  result=$(echo "$test" | jq -r '.result')
+  echo "result: $result"
+  url=$(echo "$test" | jq -r '.url')
+  echo "url: $url"
+  if [[ "$result" != "SKIP" ]]
+  then
+    stdout=$(echo "$test" | jq -r '.stdout' | base64 -d)
+    if [[ -n "$stdout" ]]
+    then
+      echo "## stdout"
+      codeblock "$stdout"
+    fi
+    stderr=$(echo "$test" | jq -r '.stderr' | base64 -d)
+    if [[ -n "$stderr" ]]
+    then
+      echo "## stderr"
+      codeblock "$stderr"
+    fi
+  fi
+  echo ""
+done
@@ -0,0 +1,168 @@
+#!/bin/bash
+
+# Run the GNU upstream test suite for diffutils against a local build of the
+# Rust implementation, print out a summary of the test results, and writes a
+# JSON file ('test-results.json') containing detailed information about the
+# test run.
+
+# The JSON file contains metadata about the test run, and for each test the
+# result as well as the contents of stdout, stderr, and of all the files
+# written by the test script, if any (excluding subdirectories).
+
+# The script takes a shortcut to fetch only the test suite from the upstream
+# repository and carefully avoids running the autotools machinery which is
+# time-consuming and resource-intensive, and doesn't offer the option to not
+# build the upstream binaries. As a consequence, the environment in which the
+# tests are run might not match exactly that used when the upstream tests are
+# run through the autotools.
+
+# Exit codes: 0 if all tests passed, 1 if at least one test failed, and 2 if
+# the test suite could not be run at all (e.g. the upstream repository couldn't
+# be fetched). Callers must treat 2 as an infrastructure error: no meaningful
+# result was produced.
+
+# By default it expects a release build of the diffutils binary, but a
+# different build profile can be specified as an argument
+# (e.g. 'dev' or 'test').
+# Unless overridden by the $TESTS environment variable, all tests in the test
+# suite will be run. Tests targeting a command that is not yet implemented
+# (e.g. diff3 or sdiff) are skipped.
+
+scriptpath=$(dirname "$(readlink -f "$0")")
+rev=$(git rev-parse HEAD)
+gnu_version="3.12"
+gnu_tarball_blake2b=5b4593b39da71578d7f975603abe9359be215b9ac76548a6ab0d6e3838bb103c7ffcddf7fa01abcd5c6289db9a2f16b43aa3d5e846a9aa4b8db866763c2660de
+
+# Report an infrastructure error: the test suite could not be run at all
+die() {
+  echo "ERROR: $*" >&2
+  exit 2
+}
+
+# Allow passing a specific profile as parameter (default to "release")
+profile="release"
+[[ -n $1 ]] && profile="$1"
+
+# Verify that the diffutils binary was built for the requested profile
+binary="$scriptpath/../target/$profile/diffutils"
+if [[ ! -x "$binary" ]]
+then
+  die "Missing build for profile $profile"
+fi
+
+# Work in a temporary directory
+tempdir=$(mktemp -d)
+trap 'rm -rf "$tempdir"' EXIT
+cd "$tempdir" || die "Cannot enter temporary directory $tempdir"
+
+# Fetch the upstream test suite
+echo "Fetching upstream test suite"
+curl -fsSL --retry 5 https://ftpmirror.gnu.org/diffutils/diffutils-${gnu_version}.tar.xz -o gnu-diffutils.tar.xz || die "Failed to fetch test suite"
+echo ${gnu_tarball_blake2b}  gnu-diffutils.tar.xz \
+ | b2sum --check || die "Failed to verify checksum of tarball of GNU diffutils"
+mkdir -p diffutils
+tar xJf gnu-diffutils.tar.xz --strip-components=1 -C diffutils || die "Failed to extract test suite"
+
+cd diffutils || die "Test suite src is broken"
+
+# Ensure that calling `diff` invokes the built `diffutils` binary instead of
+# the upstream `diff` binary that is most likely installed on the system
+cd src || die "Missing the directory holding the diff and cmp symlinks"
+ln -s "$binary" diff
+ln -s "$binary" cmp
+cd ../tests || die "Cannot enter the upstream tests directory"
+
+if [[ -n "$TESTS" ]]
+then
+  tests="$TESTS"
+else
+  # Get a list of all upstream tests (default if $TESTS isn't set)
+  echo -e '\n\nprinttests:\n\t@echo "${TESTS}"' >> Makefile.am
+  tests=$(make -f Makefile.am printtests)
+fi
+total=$(echo "$tests" | wc -w)
+(( total > 0 )) || die "No test to run: the upstream test list is empty"
+echo "Running $total tests"
+export LC_ALL=C
+export KEEP=yes
+timestamp=$(date -Iseconds)
+passed=0
+failed=0
+skipped=0
+normal="$(tput sgr0)"
+for test in $tests
+do
+  result="FAIL"
+  # Run only the tests that invoke `diff` or `cmp`,
+  # because other binaries aren't implemented yet
+  if ! grep -E -s -q "(diff3|sdiff)" "$test"
+  then
+    sh "$test" 1> stdout.txt 2> stderr.txt && result="PASS"
+    if [[ $? = 77 ]]
+    then
+      result="SKIP"
+    else
+      json+="{\"test\":\"$test\",\"result\":\"$result\","
+      json+="\"stdout\":\"$(base64 -w0 < stdout.txt)\","
+      json+="\"stderr\":\"$(base64 -w0 < stderr.txt)\","
+      json+="\"files\":{"
+      cd gt-$test.*
+      # Note: this doesn't include the contents of subdirectories,
+      # but there isn't much value added in doing so
+      for file in *
+      do
+        # Encode the name with jq: some tests create files whose name contains
+        # quotes or control characters, which would produce invalid JSON
+        [[ -f "$file" ]] && json+="$(jq -Rn --arg name "$file" '$name'):\"$(base64 -w0 < "$file")\","
+      done
+      json="${json%,}}},"
+      cd - > /dev/null
+      [[ "$result" = "PASS" ]] && (( passed++ ))
+      [[ "$result" = "FAIL" ]] && (( failed++ ))
+    fi
+  else
+    result="SKIP"
+  fi
+  color=2 # green
+  [[ "$result" = "FAIL" ]] && color=1 # red
+  if [[ $result = "SKIP" ]]
+  then
+    (( skipped++ ))
+    json+="{\"test\":\"$test\",\"result\":\"$result\"},"
+    color=3 # yellow
+  fi
+  printf "  %-40s $(tput setaf $color)$result$(tput sgr0)\n" "$test"
+done
+echo ""
+echo -n "Summary: TOTAL: $total / "
+echo -n "$(tput setaf 2)PASS$normal: $passed / "
+echo -n "$(tput setaf 1)FAIL$normal: $failed / "
+echo "$(tput setaf 3)SKIP$normal: $skipped"
+echo ""
+
+json="\"tests\":[${json%,}]"
+metadata="\"timestamp\":\"$timestamp\","
+metadata+="\"revision\":\"$rev\","
+metadata+="\"upstream-version\":\"$gnu_version\","
+if [[ -n "$GITHUB_ACTIONS" ]]
+then
+  metadata+="\"branch\":\"$GITHUB_REF\","
+fi
+json="{$metadata $json}"
+
+# Clean up
+cd "$scriptpath"
+
+# Write the results out only once they are known to be valid JSON, so that a
+# malformed (or truncated) file is never left behind for the caller to consume
+resultsfile="test-results.json"
+if ! echo "$json" | jq > "$resultsfile.tmp"
+then
+  rm -f "$resultsfile.tmp"
+  die "Generated invalid JSON results"
+fi
+mv "$resultsfile.tmp" "$resultsfile"
+echo "Results written to $scriptpath/$resultsfile"
+
+(( failed > 0 )) && exit 1
+exit 0
@@ -0,0 +1,2 @@
+diff
+cmp
@@ -0,0 +1,162 @@
+#!/usr/bin/env python3
+
+"""
+Compare the current GNU test results to the last results gathered from the main branch to
+highlight if a PR is making the results better/worse.
+Don't exit with error code if all failing tests are in the ignore-intermittent.txt list.
+
+Exit status: 0 if the comparison shows no new failure, 1 if new non-intermittent
+failures appeared, and 2 if the comparison couldn't be performed at all (e.g. one
+of the result files is missing or malformed).
+"""
+
+import json
+import sys
+import argparse
+from pathlib import Path
+
+
+def load_ignore_list(ignore_file):
+    """Load list of intermittent test names to ignore from file."""
+    ignore_set = set()
+    if ignore_file and Path(ignore_file).exists():
+        with open(ignore_file, "r") as f:
+            for line in f:
+                line = line.strip()
+                if line and not line.startswith("#"):
+                    ignore_set.add(line)
+    return ignore_set
+
+
+def extract_test_results(json_data):
+    """Extract test results from a diffutils test-results.json.
+
+    Note: unlike sed, diffutils JSON has no 'summary' object — results are
+    computed from the 'tests' array using the 'result' and 'test' fields.
+    """
+    tests = json_data.get("tests", [])
+    passed  = sum(1 for t in tests if t.get("result") == "PASS")
+    failed  = sum(1 for t in tests if t.get("result") == "FAIL")
+    skipped = sum(1 for t in tests if t.get("result") == "SKIP")
+    summary = {"total": len(tests), "passed": passed, "failed": failed, "skipped": skipped}
+    failed_tests = [t["test"] for t in tests if t.get("result") == "FAIL"]
+    return summary, failed_tests
+
+
+def compare_results(current_file, reference_file, ignore_file=None, output_file=None):
+    """Compare current results with reference results."""
+    ignore_set = load_ignore_list(ignore_file)
+
+    try:
+        with open(current_file, "r") as f:
+            current_data = json.load(f)
+        current_summary, current_failed = extract_test_results(current_data)
+    except Exception as e:
+        print(f"Error loading current results: {e}")
+        return 2
+
+    try:
+        with open(reference_file, "r") as f:
+            reference_data = json.load(f)
+        reference_summary, reference_failed = extract_test_results(reference_data)
+    except Exception as e:
+        print(f"Error loading reference results: {e}")
+        return 2
+
+    # Calculate differences
+    pass_diff  = int(current_summary.get("passed",  0)) - int(reference_summary.get("passed",  0))
+    fail_diff  = int(current_summary.get("failed",  0)) - int(reference_summary.get("failed",  0))
+    total_diff = int(current_summary.get("total",   0)) - int(reference_summary.get("total",   0))
+
+    # Find new failures and improvements
+    current_failed_set   = set(current_failed)
+    reference_failed_set = set(reference_failed)
+
+    new_failures  = current_failed_set   - reference_failed_set
+    improvements  = reference_failed_set - current_failed_set
+
+    # Filter out intermittent failures
+    non_intermittent_new_failures = new_failures - ignore_set
+
+    # Check if results are identical (no changes)
+    no_changes = (
+        pass_diff == 0
+        and fail_diff == 0
+        and total_diff == 0
+        and not new_failures
+        and not improvements
+    )
+
+    # If no changes, write empty output to prevent comment posting
+    if no_changes:
+        if output_file:
+            with open(output_file, "w") as f:
+                f.write("")
+        return 0
+
+    # Prepare output message
+    output_lines = []
+
+    output_lines.append("Test results comparison:")
+    output_lines.append(
+        f"  Current:   TOTAL: {current_summary.get('total', 0)} / PASSED: {current_summary.get('passed', 0)} / FAILED: {current_summary.get('failed', 0)} / SKIPPED: {current_summary.get('skipped', 0)}"
+    )
+    output_lines.append(
+        f"  Reference: TOTAL: {reference_summary.get('total', 0)} / PASSED: {reference_summary.get('passed', 0)} / FAILED: {reference_summary.get('failed', 0)} / SKIPPED: {reference_summary.get('skipped', 0)}"
+    )
+    output_lines.append("")
+
+    if pass_diff != 0 or fail_diff != 0 or total_diff != 0:
+        output_lines.append("Changes from main branch:")
+        output_lines.append(f"  TOTAL: {total_diff:+d}")
+        output_lines.append(f"  PASSED: {pass_diff:+d}")
+        output_lines.append(f"  FAILED: {fail_diff:+d}")
+        output_lines.append("")
+
+    if new_failures:
+        output_lines.append(f"New test failures ({len(new_failures)}):")
+        for test in sorted(new_failures):
+            if test in ignore_set:
+                output_lines.append(f"  - {test} (intermittent)")
+            else:
+                output_lines.append(f"  - {test}")
+        output_lines.append("")
+
+    if improvements:
+        output_lines.append(f"Test improvements ({len(improvements)}):")
+        for test in sorted(improvements):
+            output_lines.append(f"  + {test}")
+        output_lines.append("")
+
+    output_text = "\n".join(output_lines)
+    if output_file:
+        with open(output_file, "w") as f:
+            f.write(output_text)
+    else:
+        print(output_text)
+
+    if non_intermittent_new_failures:
+        print(
+            f"ERROR: Found {len(non_intermittent_new_failures)} new non-intermittent test failures"
+        )
+        return 1
+
+    return 0
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Compare GNU diffutils test results")
+    parser.add_argument("current",   help="Current test results JSON file")
+    parser.add_argument("reference", help="Reference test results JSON file")
+    parser.add_argument(
+        "--ignore-file", help="File containing intermittent test names to ignore"
+    )
+    parser.add_argument("--output",  help="Output file for comparison results")
+
+    args = parser.parse_args()
+
+    return compare_results(args.current, args.reference, args.ignore_file, args.output)
+
+
+if __name__ == "__main__":
+    sys.exit(main())