fix(#91): reject stale fidelity approvals

scripts/release-fidelity/verify.mjs

@@ -24,11 +24,13 @@ try {
   const candidate = text.match(/^- Candidate commit: ([0-9a-f]{40})$/mi)?.[1]
   if (!candidate) throw new Error(`${signoff} must contain a full candidate commit SHA`)
   git('cat-file', '-e', `${candidate}^{commit}`)
-  const signoffCommit = git('log', '-1', '--format=%H', 'HEAD', '--', signoff)
-  try {
-    git('merge-base', '--is-ancestor', candidate, signoffCommit)
-  } catch {
-    throw new Error(`${signoff} must be committed after candidate ${candidate}`)
+  const parent = git('rev-parse', 'HEAD^')
+  const changed = git('diff', '--name-only', 'HEAD^', 'HEAD').split('\n').filter(Boolean)
+  if (changed.length !== 1 || changed[0] !== signoff) {
+    throw new Error(`HEAD must contain only the sign-off file change: ${signoff}`)
+  }
+  if (candidate.toLowerCase() !== parent.toLowerCase()) {
+    throw new Error(`${signoff} candidate must equal HEAD^ (${parent})`)
   }
   const fields = [
     ['Version', version],

scripts/release-fidelity/verify.test.mjs

@@ -11,7 +11,14 @@ function git(directory, ...args) {
   return execFileSync('git', args, { cwd: directory, encoding: 'utf8' }).trim()
 }
 
-test('accepts a committed sign-off for an ancestor candidate', async () => {
+function verify(root, evidence) {
+  return execFileSync(process.execPath, [verifier, '--version', 'v-test', '--evidence', evidence], {
+    cwd: root,
+    encoding: 'utf8',
+  })
+}
+
+async function approvedCandidate({ changeCodeWithSignoff = false } = {}) {
   const root = await mkdtemp(join(tmpdir(), 'boxbox-fidelity-verify-'))
   git(root, 'init')
   git(root, 'config', 'user.email', 'test@example.com')
@@ -23,16 +30,41 @@ test('accepts a committed sign-off for an ancestor candidate', async () => {
 
   await mkdir(join(root, 'docs/release/owner-reviews'), { recursive: true })
   await writeFile(join(root, 'docs/release/owner-reviews/v-test.md'), `- Version: v-test\n- Candidate commit: ${candidate}\n- Reviewed by: Owner\n- Reviewed on: 2026-07-30\n- Decision: approved\n`)
+  if (changeCodeWithSignoff) await writeFile(join(root, 'candidate.txt'), 'changed with approval')
   git(root, 'add', 'docs/release/owner-reviews/v-test.md')
+  if (changeCodeWithSignoff) git(root, 'add', 'candidate.txt')
   git(root, 'commit', '-m', 'owner sign-off')
 
   const evidence = join(root, 'evidence')
   await mkdir(evidence)
   await writeFile(join(evidence, 'index.html'), '')
   await writeFile(join(evidence, 'summary.md'), '')
-  const output = execFileSync(process.execPath, [verifier, '--version', 'v-test', '--evidence', evidence], {
-    cwd: root,
-    encoding: 'utf8',
+  return { candidate, evidence, root }
+}
+
+function assertBlocked(root, evidence) {
+  assert.throws(() => verify(root, evidence), (error) => {
+    assert.match(String(error.stderr), /HEAD must contain only the sign-off file change/)
+    return true
   })
+}
+
+test('accepts a sign-off-only HEAD for its direct parent candidate', async () => {
+  const { candidate, evidence, root } = await approvedCandidate()
+  const output = verify(root, evidence)
   assert.match(output, new RegExp(candidate))
 })
+
+test('rejects code committed after approval', async () => {
+  const { evidence, root } = await approvedCandidate()
+  await writeFile(join(root, 'candidate.txt'), 'changed after review')
+  git(root, 'add', 'candidate.txt')
+  git(root, 'commit', '-m', 'code after approval')
+
+  assertBlocked(root, evidence)
+})
+
+test('rejects a sign-off commit that also changes code', async () => {
+  const { evidence, root } = await approvedCandidate({ changeCodeWithSignoff: true })
+  assertBlocked(root, evidence)
+})