BigW Consortium Gitlab
1. When a merge request is being merged, save the merge commit SHA in the `in_progress_merge_commit_sha` database column. 2. The `pre-receive` hook looks for any locked (in progress) merge request with `in_progress_merge_commit_sha` matching the `newrev` it is passed. 3. If it finds a matching MR, the merge is legitimate. 4. Update `git_access_spec` to test the behaviour we added here. Also refactored this spec a bit to make it easier to add more contexts / conditions.