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/git_ui/Cargo.toml

@@ -49,3 +49,4 @@ windows.workspace = true
 
 [features]
 default = []
+test-support = ["multi_buffer/test-support"]

crates/git_ui/src/project_diff.rs

@@ -33,7 +33,7 @@ use crate::git_panel::{GitPanel, GitPanelAddon, GitStatusEntry};
 
 actions!(git, [Diff]);
 
-pub(crate) struct ProjectDiff {
+pub struct ProjectDiff {
     multibuffer: Entity<MultiBuffer>,
     editor: Entity<Editor>,
     project: Entity<Project>,
@@ -438,6 +438,15 @@ impl ProjectDiff {
 
         Ok(())
     }
+
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn excerpt_paths(&self, cx: &App) -> Vec<String> {
+        self.multibuffer
+            .read(cx)
+            .excerpt_paths()
+            .map(|key| key.path().to_string_lossy().to_string())
+            .collect()
+    }
 }
 
 impl EventEmitter<EditorEvent> for ProjectDiff {}