Skip a HookEventPullRequestSync event if it has the same CommitSHA as an existing HookEventPullRequest event in the ActionRun table. A HookEventPullRequestSync event must only create an ActionRun if the CommitSHA is different from what it was when the PR was open.
This guards against a race that can happen when the following is done in parallel:
* A commit C is pushed to a repo on branch B
* A pull request with head on branch B
it is then possible that the pull request is created first, successfully. The commit that was just pushed is not known yet but the PR only references the repository and the B branch so it is fine.
A HookEventPullRequest event is sent to the notification queue but not processed immediately.
The commit C is pushed and processed successfully. Since the PR already exists and has a head that matches the branch, the head of the PR is updated with the commit C and a HookEventPullRequestSync event is sent to the notification queue.
The HookEventPullRequest event is processed and since the head of the PR was updated to be commit C, an ActionRun with CommitSHA C is created.
The HookEventPullRequestSync event is then processed and also has a CommitSHA equal to C.
Refs: https://codeberg.org/forgejo/forgejo/issues/2009
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/2314
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>
