[v14.0/forgejo] fix: prevent intermittent test failures caused by uncancellable tasks (#10717)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/10713

Attempt to fix intermittent test failure noted in #10633, detailed technical notes in https://codeberg.org/forgejo/forgejo/issues/10633#issuecomment-9571199.

- Failure to cancel the previous processes is now a test error that aborts immediately, preventing 2hr long test runs that won't succeed.
- When the process cancellation fails, the stack trace of all goroutines is printed to help diagnose the cause of any failure to cancel tasks.
- `context.Background()` referenced in the actions notifier is corrected when opening git repos, which seems to be a cause of failure to cancel the tasks -- git subprocesses are spawned from the repo context, which is the background context, and that prevents the context registered in the process manager from cancelling them.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests

- I added test coverage for Go changes...
  - [ ] in their respective `*_test.go` for unit tests.
  - [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [x] I do not want this change to show in the release notes.
- [ ] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.

Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10717
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>
Co-authored-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>
Co-committed-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>

services/actions/notifier_helper.go

@@ -187,8 +187,8 @@ func notify(ctx context.Context, input *notifyInput) error {
 	return handleWorkflows(ctx, detectedWorkflows, commit, input, ref.String())
 }
 
-func getGitRepoAndCommit(_ context.Context, input *notifyInput) (*git.Repository, *git.Commit, git.RefName, error) {
-	gitRepo, err := gitrepo.OpenRepository(context.Background(), input.Repo)
+func getGitRepoAndCommit(ctx context.Context, input *notifyInput) (*git.Repository, *git.Commit, git.RefName, error) {
+	gitRepo, err := gitrepo.OpenRepository(ctx, input.Repo)
 	if err != nil {
 		return nil, nil, "", fmt.Errorf("git.OpenRepository: %w", err)
 	}
@@ -598,7 +598,7 @@ func DetectAndHandleSchedules(ctx context.Context, repo *repo_model.Repository)
 		return nil
 	}
 
-	gitRepo, err := gitrepo.OpenRepository(context.Background(), repo)
+	gitRepo, err := gitrepo.OpenRepository(ctx, repo)
 	if err != nil {
 		return fmt.Errorf("git.OpenRepository: %w", err)
 	}

tests/test_utils.go

@@ -263,6 +263,11 @@ func cancelProcesses(t testing.TB, delay time.Duration) {
 			for _, p := range processes {
 				t.Logf("PrepareTestEnv:Remaining Process: %q", p.Description)
 			}
+			stacks := allGoroutineStacks()
+			t.Errorf("All goroutine stacks during process cancellation failure:\n%s", string(stacks))
+			// exit so that we don't spin in a loop executing `delay` wait over and over again when we won't be able to
+			// complete tests correctly due to the environmental issue present.
+			exitf("terminating test run due to unrecoverable failure")
 			return
 		}
 		runtime.Gosched() // let the context cancellation propagate
@@ -271,6 +276,18 @@ func cancelProcesses(t testing.TB, delay time.Duration) {
 	t.Logf("PrepareTestEnv: all processes cancelled within %s", time.Since(start))
 }
 
+// allGoroutineStacks is the same as runtime/debug.Stack(), but it captures the stack of all goroutines.
+func allGoroutineStacks() []byte {
+	buf := make([]byte, 1024)
+	for {
+		n := runtime.Stack(buf, true)
+		if n < len(buf) {
+			return buf[:n]
+		}
+		buf = make([]byte, 2*len(buf))
+	}
+}
+
 func PrepareGitRepoDirectory(t testing.TB) {
 	setting.RepoRootPath = t.TempDir()
 	require.NoError(t, unittest.CopyDir(preparedDir, setting.RepoRootPath))