Load world extensions from commit snapshots with last-good recovery

userland/exec-tools/src/revert.rs

@@ -0,0 +1,25 @@
+//! Move the world's extension branch to its last successful commit.
+fn run() -> std::io::Result<i32> {
+    let good = std::fs::read_to_string("/src/sausage/.git/sausage-last-good")?;
+    if good.trim().is_empty() {
+        return Err(std::io::Error::other("No successful extension commit"));
+    }
+    sausage_spawn::Command::new("git")
+        .args([
+            "-C",
+            "/src/sausage",
+            "update-ref",
+            "refs/heads/main",
+            good.trim(),
+        ])
+        .status()
+}
+fn main() {
+    std::process::exit(match run() {
+        Ok(code) => code,
+        Err(error) => {
+            eprintln!("extensions-revert: {error}");
+            1
+        }
+    });
+}