Use correct worktree when getting permalink to line (#8888)

Previously this code would call `project.visible_worktrees(cx).next`
which might not necessarily return the worktree matching the currently
open file.

What this change does is it adds `get_repo` method on `Project` that
allows us to get the `GitRepository` for the current buffer.

Release Notes:

- Fixed `open permalink to line` not working when multiple folders are
added to the project.

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/project_core/src/worktree.rs

@@ -2116,6 +2116,11 @@ impl LocalSnapshot {
         Some((path, self.git_repositories.get(&repo.work_directory_id())?))
     }
 
+    pub fn local_git_repo(&self, path: &Path) -> Option<Arc<Mutex<dyn GitRepository>>> {
+        self.local_repo_for_path(path)
+            .map(|(_, entry)| entry.repo_ptr.clone())
+    }
+
     fn build_update(
         &self,
         project_id: u64,