Use repository mutex more sparingly. Don't hold it while running git status. (#12489)

Previously, each git `Repository` object was held inside of a mutex.
This was needed because libgit2's Repository object is (as one would
expect) not thread safe. But now, the two longest-running git operations
that Zed performs, (`status` and `blame`) do not use libgit2 - they
invoke the `git` executable. For these operations, it's not necessary to
hold a lock on the repository.

In this PR, I've moved our mutex usage so that it only wraps the libgit2
calls, not our `git` subprocess spawns. The main user-facing impact of
this is that the UI is much more responsive when initially opening a
project with a very large git repository (e.g. `chromium`, `webkit`,
`linux`).

Release Notes:

- Improved Zed's responsiveness when initially opening a project
containing a very large git repository.

crates/project/src/project.rs

@@ -7856,10 +7856,7 @@ impl Project {
                                     None
                                 } else {
                                     let relative_path = repo.relativize(&snapshot, &path).ok()?;
-                                    local_repo_entry
-                                        .repo()
-                                        .lock()
-                                        .load_index_text(&relative_path)
+                                    local_repo_entry.repo().load_index_text(&relative_path)
                                 };
                                 Some((buffer, base_text))
                             }
@@ -8194,7 +8191,7 @@ impl Project {
         &self,
         project_path: &ProjectPath,
         cx: &AppContext,
-    ) -> Option<Arc<Mutex<dyn GitRepository>>> {
+    ) -> Option<Arc<dyn GitRepository>> {
         self.worktree_for_id(project_path.worktree_id, cx)?
             .read(cx)
             .as_local()?
@@ -8202,10 +8199,7 @@ impl Project {
             .local_git_repo(&project_path.path)
     }
 
-    pub fn get_first_worktree_root_repo(
-        &self,
-        cx: &AppContext,
-    ) -> Option<Arc<Mutex<dyn GitRepository>>> {
+    pub fn get_first_worktree_root_repo(&self, cx: &AppContext) -> Option<Arc<dyn GitRepository>> {
         let worktree = self.visible_worktrees(cx).next()?.read(cx).as_local()?;
         let root_entry = worktree.root_git_entry()?;
 
@@ -8255,8 +8249,7 @@ impl Project {
 
             cx.background_executor().spawn(async move {
                 let (repo, relative_path, content) = blame_params?;
-                let lock = repo.lock();
-                lock.blame(&relative_path, content)
+                repo.blame(&relative_path, content)
                     .with_context(|| format!("Failed to blame {:?}", relative_path.0))
             })
         } else {