git_ui: Always use latest commit message on amend (#44553)

Update the behavior of `git::Amend` to ensure that the latest head
commit message, if available, is always loaded into the commit message
editor, regardless of its state. The previous text, if any, is now also
restored after the amend is finished.

- Update `FakeGitRepository.show` to include a message in the returned
`CommitDetails` so we can assert that this specific commit message is
set in the commit message editor.
- Add default implementation for `FakeGitRepository.commit` and
`FakeGitRepository.run_hook` to ensure that tests are able to run and
don't panic on `unimplemented!()`
- Refactor `GitPanel.load_last_commit_message_if_empty` to
`GitPanel.load_last_commit_message`, ensuring that the head commit
message is always loaded, regardless of whether the commit message
editor is empty.
- Update `GitPanel.commit_changes` to ensure that the pending amend
state is only updated if the editor managed to actually commit the
changes. This also ensures that we don't restore the commit message
editor's contents when amending a commit, before the amend is actually
processed.
- Update `CommitModal.amend`, removing the call to
`GitPanel.set_amend_pending` as that is now handled by the background
task created in `GitPanel.commit_changes`.
- Split the `commit` and `amend` methods from the event handlers so that
the methods can be called directly, as is now being done by
`CommitModal.on_commit` and `CommitModal.on_amend`.

Release Notes:

- Updated the ‎`git: amend` command to always load the latest head
commit message, and to restore any previously entered text in the commit
message editor after the amend completes

crates/git_ui/src/commit_modal.rs

@@ -139,7 +139,7 @@ impl CommitModal {
                             && !git_panel.amend_pending()
                         {
                             git_panel.set_amend_pending(true, cx);
-                            git_panel.load_last_commit_message_if_empty(cx);
+                            git_panel.load_last_commit_message(cx);
                         }
                     }
                     ForceMode::Commit => {
@@ -492,53 +492,22 @@ impl CommitModal {
         }
     }
 
-    fn commit(&mut self, _: &git::Commit, window: &mut Window, cx: &mut Context<Self>) {
-        if self.git_panel.read(cx).amend_pending() {
-            return;
-        }
-        telemetry::event!("Git Committed", source = "Git Modal");
-        self.git_panel.update(cx, |git_panel, cx| {
-            git_panel.commit_changes(
-                CommitOptions {
-                    amend: false,
-                    signoff: git_panel.signoff_enabled(),
-                },
-                window,
-                cx,
-            )
-        });
-        cx.emit(DismissEvent);
-    }
-
-    fn amend(&mut self, _: &git::Amend, window: &mut Window, cx: &mut Context<Self>) {
+    fn on_commit(&mut self, _: &git::Commit, window: &mut Window, cx: &mut Context<Self>) {
         if self
             .git_panel
-            .read(cx)
-            .active_repository
-            .as_ref()
-            .and_then(|repo| repo.read(cx).head_commit.as_ref())
-            .is_none()
+            .update(cx, |git_panel, cx| git_panel.commit(window, cx))
         {
-            return;
+            telemetry::event!("Git Committed", source = "Git Modal");
+            cx.emit(DismissEvent);
         }
-        if !self.git_panel.read(cx).amend_pending() {
-            self.git_panel.update(cx, |git_panel, cx| {
-                git_panel.set_amend_pending(true, cx);
-                git_panel.load_last_commit_message_if_empty(cx);
-            });
-        } else {
+    }
+
+    fn on_amend(&mut self, _: &git::Amend, window: &mut Window, cx: &mut Context<Self>) {
+        if self
+            .git_panel
+            .update(cx, |git_panel, cx| git_panel.amend(window, cx))
+        {
             telemetry::event!("Git Amended", source = "Git Modal");
-            self.git_panel.update(cx, |git_panel, cx| {
-                git_panel.set_amend_pending(false, cx);
-                git_panel.commit_changes(
-                    CommitOptions {
-                        amend: true,
-                        signoff: git_panel.signoff_enabled(),
-                    },
-                    window,
-                    cx,
-                );
-            });
             cx.emit(DismissEvent);
         }
     }
@@ -564,8 +533,8 @@ impl Render for CommitModal {
             .id("commit-modal")
             .key_context("GitCommit")
             .on_action(cx.listener(Self::dismiss))
-            .on_action(cx.listener(Self::commit))
-            .on_action(cx.listener(Self::amend))
+            .on_action(cx.listener(Self::on_commit))
+            .on_action(cx.listener(Self::on_amend))
             .when(!DisableAiSettings::get_global(cx).disable_ai, |this| {
                 this.on_action(cx.listener(|this, _: &GenerateCommitMessage, _, cx| {
                     this.git_panel.update(cx, |panel, cx| {