fix(source-control): show git history commit times to the second (#23954)

src/renderer/src/components/right-sidebar/source-control/sync/git-history-format.test.ts

@@ -0,0 +1,38 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { formatGitHistoryTimestamp } from './git-history-format'
+
+const commitTime = Date.UTC(2026, 5, 15, 12, 30, 45)
+
+// Assert distinctness rather than literal strings: output follows the runner's locale and time zone.
+describe('formatGitHistoryTimestamp', () => {
+  it.each([
+    ['one second apart', commitTime + 1000],
+    ['on the same day in different years', Date.UTC(2025, 5, 15, 12, 30, 45)]
+  ])('tells apart commits %s', (_label, otherTime) => {
+    expect(formatGitHistoryTimestamp(commitTime)).not.toBe(formatGitHistoryTimestamp(otherTime))
+  })
+})
+
+// Node reads the OS timezone on Windows and ignores a runtime process.env.TZ change, so the
+// stub — and the precondition asserting it took — cannot work there.
+describe.skipIf(process.platform === 'win32')('formatGitHistoryTimestamp local-time zone', () => {
+  afterEach(() => {
+    vi.unstubAllEnvs()
+  })
+
+  it('tells apart commits in the hour a DST fall-back repeats', async () => {
+    vi.stubEnv('TZ', 'America/New_York')
+    // Precondition: the stub took and 2026-11-01 really does replay an hour here.
+    expect(new Date(2026, 10, 1, 12).getTimezoneOffset()).toBe(
+      new Date(2026, 10, 1, 0).getTimezoneOffset() + 60
+    )
+    // The formatter binds the time zone when the module loads, so load it under the stub.
+    vi.resetModules()
+    const { formatGitHistoryTimestamp: formatInNewYork } = await import('./git-history-format')
+
+    // 1:30 AM EDT, then 1:30 AM EST an hour later.
+    expect(formatInNewYork(Date.UTC(2026, 10, 1, 5, 30))).not.toBe(
+      formatInNewYork(Date.UTC(2026, 10, 1, 6, 30))
+    )
+  })
+})

src/renderer/src/components/right-sidebar/source-control/sync/git-history-format.ts

@@ -1,6 +1,7 @@
+// Why: the zone name disambiguates the repeated hour when clocks fall back.
 const gitHistoryTimestampFormatter = new Intl.DateTimeFormat(undefined, {
-  month: 'short',
-  day: 'numeric'
+  dateStyle: 'medium',
+  timeStyle: 'long'
 })
 
 export function formatGitHistoryTimestamp(timestamp: number | undefined): string {