fix: focus After when opening a diff file

src/diff.rs

@@ -1151,7 +1151,8 @@ impl DiffState {
                     if let Some(path) = files.accept()
                         && self.select_file(&path)
                     {
-                        self.focus = self.first_text_focus();
+                        self.focus = Focus::After;
+                        self.normalize_focus();
                         let files = self.files.as_mut().expect("comparison picker");
                         files.focused = false;
                         self.files_visible = files.presentation == FilePresentation::Docked;
@@ -3205,6 +3206,55 @@ mod tests {
         );
     }
 
+    #[test]
+    fn opening_diff_file_focuses_after_when_present() {
+        for view_mode in [ViewMode::Split, ViewMode::Unified] {
+            for presentation in [FilePresentation::Docked, FilePresentation::Floating] {
+                for status in [
+                    FileStatus::Modified,
+                    FileStatus::Renamed,
+                    FileStatus::Added,
+                    FileStatus::Removed,
+                ] {
+                    let mut editor = editor();
+                    editor.set_diff_display_options(view_mode, crate::panes::SplitAxis::Vertical);
+                    open(&mut editor);
+                    let id = choose_pair(&mut editor);
+                    let mut changes = comparison();
+                    let index = match status {
+                        FileStatus::Modified | FileStatus::Renamed => 0,
+                        FileStatus::Added => 1,
+                        FileStatus::Removed => 2,
+                    };
+                    let mut file = changes.files.remove(index);
+                    file.status = status;
+                    let expected_text = file.after.join("\n");
+                    changes.files = vec![file];
+                    editor.apply_diff_result(id, Ok(Outcome::Comparison(changes)));
+                    if presentation == FilePresentation::Floating {
+                        text(&mut editor, " o");
+                    }
+                    editor.handle(Input::Enter);
+                    let diff = editor.diff().unwrap();
+                    assert_eq!(
+                        diff.focus,
+                        if status == FileStatus::Removed {
+                            Focus::Before
+                        } else {
+                            Focus::After
+                        },
+                        "{view_mode:?} {presentation:?} {status:?}",
+                    );
+                    assert!(!diff.files.as_ref().unwrap().focused);
+                    assert_eq!(diff.files_visible, presentation == FilePresentation::Docked);
+                    if status != FileStatus::Removed {
+                        assert_eq!(editor.context().text, expected_text);
+                    }
+                }
+            }
+        }
+    }
+
     #[test]
     fn added_file_picker_cancel_close_and_mouse_focus_use_after() {
         let mut editor = editor();
@@ -3509,7 +3559,7 @@ mod tests {
         assert!(!picker.entries().nth(picker.selected).unwrap().is_dir);
         editor.handle(Input::Enter);
         assert_eq!(editor.diff().unwrap().file, 0);
-        editor.handle(Input::BackTab);
+        text(&mut editor, " e");
         editor.handle(Input::Char('i'));
         text(&mut editor, "x/y");
         editor.handle(Input::Enter);

src/tui.rs

@@ -8675,6 +8675,7 @@ mod tests {
         let mut diff = diff_comparison(vec![deletion_file(), added]);
         diff.handle(Input::Down);
         diff.handle(Input::Enter);
+        diff.handle(Input::BackTab);
         for _ in 0..4 {
             diff.handle(Input::Right);
         }