git_ui: Better handle commit message amend (#35268)

Follow up to this: #35114

* Previously we were still showing the commit message even after
cancelling amend which was the old commit message.
* This PR fixes that by restoring the commit message to the old state
before the amend begin so that in case user typed a commit message it's
shown if not then it's not.

Before:


https://github.com/user-attachments/assets/e0edcfff-863d-4367-a7c4-8a2998e702ca

After:



https://github.com/user-attachments/assets/9daf9be0-8a3d-4914-91a4-567693711b6b




Release Notes:

- Resolved an issue where cancelling an amend commit would incorrectly
leave the old commit message in the input field. The commit message box
now properly reverts to its pre-amend state.

crates/git_ui/src/git_panel.rs

@@ -351,6 +351,7 @@ pub struct GitPanel {
     pending: Vec<PendingOperation>,
     pending_commit: Option<Task<()>>,
     amend_pending: bool,
+    original_commit_message: Option<String>,
     signoff_enabled: bool,
     pending_serialization: Task<()>,
     pub(crate) project: Entity<Project>,
@@ -532,6 +533,7 @@ impl GitPanel {
                 pending: Vec::new(),
                 pending_commit: None,
                 amend_pending: false,
+                original_commit_message: None,
                 signoff_enabled: false,
                 pending_serialization: Task::ready(()),
                 single_staged_entry: None,
@@ -1713,6 +1715,7 @@ impl GitPanel {
                     Ok(()) => {
                         this.commit_editor
                             .update(cx, |editor, cx| editor.clear(window, cx));
+                        this.original_commit_message = None;
                     }
                     Err(e) => this.show_error_toast("commit", e, cx),
                 }
@@ -4345,6 +4348,22 @@ impl GitPanel {
     }
 
     pub fn set_amend_pending(&mut self, value: bool, cx: &mut Context<Self>) {
+        if value && !self.amend_pending {
+            let current_message = self.commit_message_buffer(cx).read(cx).text();
+            self.original_commit_message = if current_message.trim().is_empty() {
+                None
+            } else {
+                Some(current_message)
+            };
+        } else if !value && self.amend_pending {
+            let message = self.original_commit_message.take().unwrap_or_default();
+            self.commit_message_buffer(cx).update(cx, |buffer, cx| {
+                let start = buffer.anchor_before(0);
+                let end = buffer.anchor_after(buffer.len());
+                buffer.edit([(start..end, message)], None, cx);
+            });
+        }
+
         self.amend_pending = value;
         self.serialize(cx);
         cx.notify();
@@ -5490,4 +5509,73 @@ mod tests {
             ],
         );
     }
+
+    #[gpui::test]
+    async fn test_amend_commit_message_handling(cx: &mut TestAppContext) {
+        init_test(cx);
+        let fs = FakeFs::new(cx.background_executor.clone());
+        fs.insert_tree(
+            "/root",
+            json!({
+                "project": {
+                    ".git": {},
+                    "src": {
+                        "main.rs": "fn main() {}"
+                    }
+                }
+            }),
+        )
+        .await;
+
+        fs.set_status_for_repo(
+            Path::new(path!("/root/project/.git")),
+            &[(Path::new("src/main.rs"), StatusCode::Modified.worktree())],
+        );
+
+        let project = Project::test(fs.clone(), [Path::new(path!("/root/project"))], cx).await;
+        let workspace =
+            cx.add_window(|window, cx| Workspace::test_new(project.clone(), window, cx));
+        let cx = &mut VisualTestContext::from_window(*workspace, cx);
+
+        let panel = workspace.update(cx, GitPanel::new).unwrap();
+
+        // Test: User has commit message, enables amend (saves message), then disables (restores message)
+        panel.update(cx, |panel, cx| {
+            panel.commit_message_buffer(cx).update(cx, |buffer, cx| {
+                let start = buffer.anchor_before(0);
+                let end = buffer.anchor_after(buffer.len());
+                buffer.edit([(start..end, "Initial commit message")], None, cx);
+            });
+
+            panel.set_amend_pending(true, cx);
+            assert!(panel.original_commit_message.is_some());
+
+            panel.set_amend_pending(false, cx);
+            let current_message = panel.commit_message_buffer(cx).read(cx).text();
+            assert_eq!(current_message, "Initial commit message");
+            assert!(panel.original_commit_message.is_none());
+        });
+
+        // Test: User has empty commit message, enables amend, then disables (clears message)
+        panel.update(cx, |panel, cx| {
+            panel.commit_message_buffer(cx).update(cx, |buffer, cx| {
+                let start = buffer.anchor_before(0);
+                let end = buffer.anchor_after(buffer.len());
+                buffer.edit([(start..end, "")], None, cx);
+            });
+
+            panel.set_amend_pending(true, cx);
+            assert!(panel.original_commit_message.is_none());
+
+            panel.commit_message_buffer(cx).update(cx, |buffer, cx| {
+                let start = buffer.anchor_before(0);
+                let end = buffer.anchor_after(buffer.len());
+                buffer.edit([(start..end, "Previous commit message")], None, cx);
+            });
+
+            panel.set_amend_pending(false, cx);
+            let current_message = panel.commit_message_buffer(cx).read(cx).text();
+            assert_eq!(current_message, "");
+        });
+    }
 }