Clear pending staged/unstaged diff hunks hunks when writing to the git index fails (#26173)

Release Notes:

- Git Beta: Fixed a bug where discarding a hunk in the project diff view
performed two concurrent saves of the buffer.
- Git Beta: Fixed an issue where diff hunks appeared in the wrong state
after failing to write to the git index.

crates/git_ui/src/git_panel.rs

@@ -307,6 +307,13 @@ impl GitPanel {
                         this.active_repository = git_store.read(cx).active_repository();
                         this.schedule_update(true, window, cx);
                     }
+                    GitEvent::IndexWriteError(error) => {
+                        this.workspace
+                            .update(cx, |workspace, cx| {
+                                workspace.show_error(error, cx);
+                            })
+                            .ok();
+                    }
                 },
             )
             .detach();

crates/git_ui/src/project_diff.rs

@@ -19,7 +19,10 @@ use gpui::{
 };
 use language::{Anchor, Buffer, Capability, OffsetRangeExt};
 use multi_buffer::{MultiBuffer, PathKey};
-use project::{git::GitStore, Project, ProjectPath};
+use project::{
+    git::{GitEvent, GitStore},
+    Project, ProjectPath,
+};
 use std::any::{Any, TypeId};
 use theme::ActiveTheme;
 use ui::{prelude::*, vertical_divider, Tooltip};
@@ -141,8 +144,13 @@ impl ProjectDiff {
         let git_store_subscription = cx.subscribe_in(
             &git_store,
             window,
-            move |this, _git_store, _event, _window, _cx| {
-                *this.update_needed.borrow_mut() = ();
+            move |this, _git_store, event, _window, _cx| match event {
+                GitEvent::ActiveRepositoryChanged
+                | GitEvent::FileSystemUpdated
+                | GitEvent::GitStateUpdated => {
+                    *this.update_needed.borrow_mut() = ();
+                }
+                _ => {}
             },
         );
 
@@ -1017,9 +1025,6 @@ mod tests {
         editor.update_in(cx, |editor, window, cx| {
             editor.git_restore(&Default::default(), window, cx);
         });
-        fs.with_git_state(path!("/project/.git").as_ref(), true, |state| {
-            state.statuses = HashMap::default();
-        });
         cx.run_until_parked();
 
         assert_state_with_diff(&editor, cx, &"ˇ".unindent());