docs/data/reusables/pull_requests/security-changes-mergeability.md

[!NOTE] If you select Dismiss stale pull request approvals when new commits are pushed and/or Require approval of the most recent reviewable push, manually creating the merge commit for a pull request and pushing it directly to a protected branch will fail, unless the contents of the merge exactly match the merge generated by {% data variables.product.prodname_dotcom %} for the pull request.

In addition, with these settings, approving reviews will be dismissed as stale if the merge base introduces new changes after the review was submitted. The merge base is the commit that is the last common ancestor between the topic branch and the base branch. If the merge base changes, the pull request cannot be merged until someone approves the work again.