Improve the git diff preview from the file viewer

test/git-two-rows.test.tsx

@@ -103,7 +103,7 @@ describe('a file that is staged and then edited again', () => {
     expect(splitText(c, 'right')).toEqual(['a', 'STAGED', 'c', 'AFTER-STAGING'])
   })
 
-  it('the picked panel behind Actual always reaches back to HEAD', async () => {
+  it('the Diff opened from Actual always reaches back to HEAD', async () => {
     const c = await boot()
     fireEvent.click(group(c, 'Changes')[0])
     const scroll = await waitFor(() => {
@@ -113,17 +113,9 @@ describe('a file that is staged and then edited again', () => {
     })
     // Line 2 is 'STAGED'. Unwrapped, its band runs from 10 + (2-1)*20.
     fireEvent.click(scroll, { clientY: 10 + 20 + 5 })
-    const peek = await waitFor(() => {
-      const p = c.querySelector<HTMLElement>('.peek')
-      if (!p) throw new Error('peek not ready')
-      return p
-    })
-    const removed = Array.from(peek.querySelectorAll('.ln-row.del'))
-    expect(removed.map((el) => el.textContent?.replace(/^\d+/, ''))).toEqual(['b'])
-
-    // A click anywhere off the code drops it.
-    fireEvent.mouseDown(document.body)
-    await waitFor(() => expect(c.querySelector('.peek')).toBeNull())
+    await waitFor(() => expect(c.querySelector('.split-overlay')).toBeTruthy())
+    expect(splitText(c, 'left')).toEqual(['a', 'b', 'c', ''])
+    expect(splitText(c, 'right')).toEqual(['a', 'STAGED', 'c', 'AFTER-STAGING'])
   })
 
   it('labels which pair the diff is comparing', async () => {