fix(docs): fork checkout needs allow-unsafe-pr-checkout; name only the surfaces that exist

- The pull_request_target fallback could not work as documented: since
  actions/checkout v7 the step refuses to place fork code in such a job
  without allow-unsafe-pr-checkout: true, so the workflow never reached
  this action. The input is now in the example, and the warning is
  rewritten around what checkout itself says: the job holds the base
  repository's token, secrets, cache scope and runner, and the switch is
  how you acknowledge that.
- The fork skip warning promised findings "in this job's summary" even
  with job-summary: false, where no summary is written. It now names the
  annotations alone in that case. A test pins both wordings and fails on
  the previous unconditional text.
- The log excerpt in the docs gets a text language tag (MD040).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018xYa7m3qup5wyN5MaXFgf6

Author: shenxianpeng

docs/fork-pr-comments.md

@@ -19,12 +19,15 @@ Everything except the comment. The action does not degrade on a fork PR:
 So a contributor pushing to a fork already gets the red check, the per-finding annotations
 on their diff, and the whole report in the job summary. The action says so in the log:
 
-```
+```text
 ::warning::Skipping PR comment: pull requests from forked repositories cannot write
 comments via the pull_request event (GITHUB_TOKEN is read-only for forks). The findings
 are in this job's summary and in the annotations on the Files changed tab.
 ```
 
+(with `job-summary: false` the message names the annotations alone, since there is no
+summary to read.)
+
 The run is **not** failed by this: `pr-comments: true` on a fork PR is a no-op, not an error.
 
 ## If you want feedback on the pull request itself
@@ -73,6 +76,10 @@ jobs:
         with:
           ref: refs/pull/${{ github.event.number }}/merge   # the PR's commits
           fetch-depth: 0
+          # Required since checkout v7: without it the step refuses to place
+          # fork code in a pull_request_target job, and this workflow never
+          # reaches the action below.
+          allow-unsafe-pr-checkout: true
       - uses: commit-check/commit-check-action@v2
         with:
           message: true
@@ -81,11 +88,15 @@ jobs:
 ```
 
 > [!WARNING]
-> `pull_request_target` grants a writable token to a workflow whose checkout contains the
-> fork's code. commit-check only *reads* commit metadata and never executes the checked-out
-> tree, but any other step you add to this job runs with that token. Keep the job to the
-> checkout and this action, never cache or build from it, and never expose secrets to it.
-> See [GitHub's guidance on `pull_request_target`](https://securitylab.github.com/resources/github-actions-preventing-pwn-requests/).
+> This is the "pwn request" shape, and `allow-unsafe-pr-checkout: true` is the switch
+> `actions/checkout` makes you flip to acknowledge it. The job runs with the base
+> repository's `GITHUB_TOKEN`, its secrets, its cache scope and its runner, and the
+> checkout puts the fork's code on that runner. commit-check only *reads* commit metadata
+> and never executes the checked-out tree, but any other step you add to this job would.
+> Keep the job to exactly these two steps, never build, install or cache from the tree,
+> and never expose secrets to it. Read
+> [Securely using `pull_request_target`](https://gh.io/securely-using-pull_request_target)
+> before turning this on.
 
 ## What this page used to describe
 

main.py

@@ -1477,11 +1477,15 @@ def add_pr_comments(results: list[ScopeResult]) -> int:
     # the GitHub API will always reject comment writes with 403.
     # pull_request_target events always have the configured token permissions.
     if is_fork_pr_with_readonly_token():
+        # Name only the surfaces this run actually produced: with
+        # job-summary: false there is no summary to send the reader to.
+        where = "in the annotations on the Files changed tab"
+        if JOB_SUMMARY_ENABLED and GITHUB_STEP_SUMMARY:
+            where = f"in this job's summary and {where}"
         msg = (
             "Skipping PR comment: pull requests from forked repositories "
             "cannot write comments via the pull_request event (GITHUB_TOKEN is "
-            "read-only for forks). The findings are in this job's summary and "
-            "in the annotations on the Files changed tab. "
+            f"read-only for forks). The findings are {where}. "
             "See https://github.com/commit-check/commit-check-action/blob/main/docs/fork-pr-comments.md"
         )
         print(f"::warning::{msg}")

main_test.py

@@ -1900,6 +1900,37 @@ def test_fork_pr_skips_comment_and_warns(self):
         self.assertIn("::warning::", printed)
         self.assertIn("read-only", printed)
 
+    def test_fork_pr_warning_names_only_the_surfaces_that_exist(self):
+        """With job-summary: false the warning must not send the reader to a
+        summary this run never wrote; the annotations are still named."""
+        summary_path = os.path.join(tempfile.mkdtemp(), "summary.txt")
+        with (
+            patch("main.PR_COMMENTS_ENABLED", True),
+            patch.dict(os.environ, {"GITHUB_EVENT_NAME": "pull_request"}),
+            patch("main.is_fork_pr", return_value=True),
+            patch("main.JOB_SUMMARY_ENABLED", False),
+            patch("main.GITHUB_STEP_SUMMARY", summary_path),
+            patch("builtins.print") as mock_print,
+        ):
+            rc = main.add_pr_comments([pass_scope()])
+        self.assertEqual(rc, 0)
+        printed = mock_print.call_args[0][0]
+        self.assertIn("annotations on the Files changed tab", printed)
+        self.assertNotIn("job's summary", printed)
+        self.assertFalse(os.path.exists(summary_path))
+
+        with (
+            patch("main.PR_COMMENTS_ENABLED", True),
+            patch.dict(os.environ, {"GITHUB_EVENT_NAME": "pull_request"}),
+            patch("main.is_fork_pr", return_value=True),
+            patch("main.JOB_SUMMARY_ENABLED", True),
+            patch("main.GITHUB_STEP_SUMMARY", summary_path),
+            patch("builtins.print") as mock_print,
+        ):
+            main.add_pr_comments([pass_scope()])
+        printed = mock_print.call_args[0][0]
+        self.assertIn("in this job's summary and in the annotations", printed)
+
     def test_fork_pr_writes_job_summary_hint(self):
         summary_path = os.path.join(tempfile.mkdtemp(), "summary.txt")
         with (