Fix some syncing issues with git statuses (#25535)

Like the real app, this one infinite loops if you have a diff in an
UnsharedFile.

Release Notes:

- N/A *or* Added/Fixed/Improved ...

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/multi_buffer/src/multi_buffer.rs

@@ -165,6 +165,10 @@ impl PathKey {
     pub fn namespaced(namespace: &'static str, path: Arc<Path>) -> Self {
         Self { namespace, path }
     }
+
+    pub fn path(&self) -> &Arc<Path> {
+        &self.path
+    }
 }
 
 pub type MultiBufferPoint = Point;
@@ -1453,6 +1457,11 @@ impl MultiBuffer {
             excerpt.range.context.start,
         ))
     }
+
+    pub fn excerpt_paths(&self) -> impl Iterator<Item = &PathKey> {
+        self.buffers_by_path.keys()
+    }
+
     /// Sets excerpts, returns `true` if at least one new excerpt was added.
     pub fn set_excerpts_for_path(
         &mut self,