We just configured our pulpcore repository to allow activating auto-merge. This goes together with suitable branch protection, depending on passing test runs and automatic dismissal of stale approvals.
So if you see your already approved pr loosing the approval after pushing “one last change”, that is why. Do not be alarmed, this is on purpose. After a push, what was approved is no longer what would have been merged anyway. So pleas kindly ask for re-review.
On the other side of the table, please remember whatever you approve is exactly what you would accept to be merged. We no make the person (or automation) to push the merge have a last say in whether something may enter the main branch. If you want “just that one last thing to change”, do not approve yet.