Add writable /self alias alongside /public and /data

cli/src/world.rs

@@ -1,6 +1,7 @@
 //! On-disk layout of a Sausage world. The folder is the source of truth:
 //! `sausage run` boots every actor that it finds in `actor/`, and then
-//! watches the folder (`watch.rs`).
+//! watches the folder (`watch.rs`). `/self` aliases the running actor's folder;
+//! `/public` and `/data` remain aliases for its `public/` and `data/`.
 //!
 //! ```text
 //! <world>/              mounted at /, readable and writable by every actor
@@ -194,7 +195,8 @@ impl World {
     /// Map a path in an actor's namespace to a host path.
     ///
     /// - Absolute paths are relative to the world root.
-    /// - `/public/...` and `/data/...` alias `sender`'s folders.
+    /// - `/self/...` aliases `sender`'s folder; `/public/...` and `/data/...`
+    ///   alias its corresponding children.
     /// - Native senders (the console) can also give absolute host paths.
     pub fn resolve(&self, sender: &str, path: &str) -> Result<PathBuf> {
         let under = |base: PathBuf, rest: &str| -> Result<PathBuf> {
@@ -214,6 +216,9 @@ impl World {
         if let Some(rest) = prefixed("/actor") {
             return under(self.actors_root(), rest);
         }
+        if let Some(rest) = prefixed("/self") {
+            return under(self.actor_dir(sender), rest);
+        }
         if let Some(rest) = prefixed("/public") {
             return under(self.public_dir(sender), rest);
         }