feat: render no-changes UI message

It's a little confusing when the calling program provides no changes in the UI, which is probably a bug in the caller, but worth explaining explicitly anyways.

src/ui.rs

@@ -2301,8 +2301,28 @@ impl Component for CommitView<'_> {
  file_views,
  } = self;
 
- let mut y = y;
  let commit_message_view_rect = viewport.draw_component(x, y, commit_message_view);
+ if file_views.is_empty() {
+ let message = "There are no changes to view.";
+ let message_rect = centered_rect(
+ Rect {
+ x,
+ y,
+ width: viewport.mask_rect().width,
+ height: viewport.mask_rect().height,
+ },
+ RectSize {
+ width: message.len(),
+ height: 1,
+ },
+ 50,
+ 50,
+ );
+ viewport.draw_text(message_rect.x, message_rect.y, &Span::raw(message));
+ return;
+ }
+
+ let mut y = y;
  y += commit_message_view_rect.height.unwrap_isize();
  for file_view in file_views {
  let file_view_rect = {

tests/test_scm_record.rs

@@ -2726,3 +2726,31 @@ fn test_deserialize() -> eyre::Result<()> {
  assert_eq!(example_contents(), deserialized);
  Ok(())
 }
+
+#[test]
+fn test_no_files() -> eyre::Result<()> {
+ let state = RecordState {
+ is_read_only: false,
+ commits: Default::default(),
+ files: vec![],
+ };
+ let initial = TestingScreenshot::default();
+ let mut input = TestingInput::new(
+ 80,
+ 6,
+ [Event::ExpandAll, initial.event(), Event::QuitAccept],
+ );
+ let recorder = Recorder::new(state, &mut input);
+ recorder.run()?;
+
+ insta::assert_display_snapshot!(initial, @r###"
+ "[File] [Edit] [Select] [View] "
+ " "
+ " There are no changes to view. "
+ " "
+ " "
+ " "
+ "###);
+
+ Ok(())
+}