workspace: Do not scan for .gitignore files if a .git directory is encountered along the way (#3135)

Partially fixes zed-industries/community#575

This PR will see one more fix to the case I've spotted while working on
this: namely, if a project has several nested repositories, e.g for a
structure:
/a
/a/.git/
/a/.gitignore
/a/b/
/a/b/.git/
/a/b/.gitignore

/b/ should not account for a's .gitignore at all - which is sort of
similar to the fix in commit #c416fbb, but for the paths in the project.

The release note is kinda bad, I'll try to reword it too.
- [ ] Improve release note.
- [x] Address the same bug for project files.

Release Notes:
- Fixed .gitignore files beyond the first .git directory being respected
by the worktree (zed-industries/community#575).

crates/project/src/worktree.rs

@@ -2027,13 +2027,18 @@ impl LocalSnapshot {
 
     fn ignore_stack_for_abs_path(&self, abs_path: &Path, is_dir: bool) -> Arc<IgnoreStack> {
         let mut new_ignores = Vec::new();
-        for ancestor in abs_path.ancestors().skip(1) {
+        for (index, ancestor) in abs_path.ancestors().enumerate() {
+            if index > 0 {
                 if let Some((ignore, _)) = self.ignores_by_parent_abs_path.get(ancestor) {
                     new_ignores.push((ancestor, Some(ignore.clone())));
                 } else {
                     new_ignores.push((ancestor, None));
                 }
             }
+            if ancestor.join(&*DOT_GIT).is_dir() {
+                break;
+            }
+        }
 
         let mut ignore_stack = IgnoreStack::none();
         for (parent_abs_path, ignore) in new_ignores.into_iter().rev() {
@@ -2048,7 +2053,6 @@ impl LocalSnapshot {
         if ignore_stack.is_abs_path_ignored(abs_path, is_dir) {
             ignore_stack = IgnoreStack::all();
         }
-
         ignore_stack
     }
 
@@ -3064,8 +3068,10 @@ impl BackgroundScanner {
 
         // Populate ignores above the root.
         let root_abs_path = self.state.lock().snapshot.abs_path.clone();
-        for ancestor in root_abs_path.ancestors().skip(1) {
-            if let Ok(ignore) = build_gitignore(&ancestor.join(&*GITIGNORE), self.fs.as_ref()).await
+        for (index, ancestor) in root_abs_path.ancestors().enumerate() {
+            if index != 0 {
+                if let Ok(ignore) =
+                    build_gitignore(&ancestor.join(&*GITIGNORE), self.fs.as_ref()).await
                 {
                     self.state
                         .lock()
@@ -3074,6 +3080,11 @@ impl BackgroundScanner {
                         .insert(ancestor.into(), (ignore.into(), false));
                 }
             }
+            if ancestor.join(&*DOT_GIT).is_dir() {
+                // Reached root of git repository.
+                break;
+            }
+        }
 
         let (scan_job_tx, scan_job_rx) = channel::unbounded();
         {