T24c round 1 fix

- FileChangeCard's header wraps: the path keeps label_width, counts and
  verdict drop below as one group; MultiFileDiffReview's header wraps its
  counts and its all-buttons inside the box, parted by justify_between
- git::DiffViewer's fold rows are Tab stops with a focus ring when the
  owner opens folds; every row keeps a transparent border so heights match;
  an inert fold no longer shows a pointer
- tests: a_narrow_review_wraps_its_rows_inside_its_box,
  git::a_fold_opens_from_the_keyboard; the gallery adds a 280px review
- AGENTS: taffy drops gaps beside an auto margin; wrapping headers

src/git/mod.rs

@@ -10,6 +10,8 @@ mod merging;
 mod refs;
 mod review;
 mod tags;
+#[cfg(all(test, feature = "test-support"))]
+mod tests;
 mod viewer;
 
 pub use badges::{DiffStat, GitStatusBadge};

src/git/tests.rs

@@ -0,0 +1,52 @@
+use gpui::{
+    Context, IntoElement, KeyBinding, KeyUpEvent, Keystroke, ParentElement, Render, Styled,
+    TestAppContext, VisualTestContext, Window, div, px,
+};
+
+use super::DiffViewer;
+use crate::{forms, primitives::FocusNext, theme::Theme};
+
+/// A diff whose first stretch folds, and the folds asked open.
+struct Folded {
+    opened: Vec<usize>,
+}
+
+impl Render for Folded {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let view = cx.entity();
+        let old: String = (0..20).map(|ix| format!("line {ix}\n")).collect();
+        let new = old.replace("line 18", "line eighteen");
+        div().w(px(480.0)).h(px(320.0)).child(
+            DiffViewer::new("diff", "a.rs", &old, &new)
+                .headless()
+                .on_open(move |ix, _, cx| view.update(cx, |folded, _| folded.opened.push(ix))),
+        )
+    }
+}
+
+fn settle(cx: &mut VisualTestContext) {
+    cx.run_until_parked();
+    cx.update(|window, _| window.refresh());
+    cx.run_until_parked();
+}
+
+#[gpui::test]
+fn a_fold_opens_from_the_keyboard(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        forms::bind_keys(cx);
+        cx.bind_keys([KeyBinding::new("tab", FocusNext, None)]);
+    });
+    let (view, cx) = cx.add_window_view(|_, _| Folded { opened: Vec::new() });
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    cx.update(|window, _| window.focus_next());
+    settle(cx);
+    cx.simulate_keystrokes("enter");
+    settle(cx);
+    cx.simulate_event(KeyUpEvent {
+        keystroke: Keystroke::parse("enter").expect("a key"),
+    });
+    settle(cx);
+    assert_eq!(view.read_with(cx, |folded, _| folded.opened.clone()), [0]);
+}

src/git/viewer.rs

@@ -3,7 +3,7 @@ use std::{ops::Range, rc::Rc};
 use gpui::{
     AnyElement, App, ElementId, FontWeight, HighlightStyle, Hsla, InteractiveElement, IntoElement,
     MouseButton, ParentElement, RenderOnce, SharedString, StatefulInteractiveElement, Styled,
-    StyledText, Window, div, prelude::*, relative, uniform_list,
+    StyledText, Window, div, prelude::*, relative, transparent_black, uniform_list,
 };
 
 use super::{
@@ -13,6 +13,7 @@ use super::{
 use crate::{
     buttons::SegmentedControl,
     editor::{code_colors, stack},
+    primitives::FocusRing,
     theme::{ActiveTheme, ControlSize, Palette, TextSize},
     typography::{LEADING, format},
 };
@@ -243,6 +244,8 @@ impl RenderOnce for DiffViewer {
                             .w_full()
                             .flex()
                             .px_2()
+                            .border_1()
+                            .border_color(transparent_black())
                             .whitespace_nowrap()
                             .line_height(relative(LEADING));
                         match &rows[ix] {
@@ -287,13 +290,17 @@ impl RenderOnce for DiffViewer {
                                     .justify_center()
                                     .bg(colors.hover.opacity(0.5))
                                     .text_color(colors.fg_subtle)
-                                    .cursor_pointer()
-                                    .hover(|row| row.text_color(colors.fg))
-                                    .on_mouse_down(MouseButton::Left, |_, window, _| {
-                                        window.prevent_default()
-                                    })
                                     .when_some(open, |row, open| {
-                                        row.on_click(move |_, window, cx| open(stretch, window, cx))
+                                        row.tab_index(0)
+                                            .focus_ring(cx)
+                                            .cursor_pointer()
+                                            .hover(|row| row.text_color(colors.fg))
+                                            .on_mouse_down(MouseButton::Left, |_, window, _| {
+                                                window.prevent_default()
+                                            })
+                                            .on_click(move |_, window, cx| {
+                                                open(stretch, window, cx)
+                                            })
                                     })
                                     .child(format!(
                                         "⋯ {}",