stack-merge feedback: If CI is bypassed by admin at GitHub, git-spice gets stuck

[danilofuchs]

If, midway through a git-spice stack merge, a GitHub admin skips CI checks and merges the bottom-most PR into main, git-spice keeps waiting indefinitely.

Perhaps git-spice should be idempotent. If the merge happens outside of the CLI, it should be detected and accepted as a success, and move on to the next PR in the stack.

We use this override to avoid running redundant CI checks during squash+merge of multiple PRs

[chagas42]

I work with @danilofuchs and was involved in the workflow that led to this
report. I’ve been looking into the local merge queue implementation, and
I’d be happy to work on a fix.

My initial idea is to make readiness polling detect when a CR has been
merged externally and treat that as an idempotent success. The merge
requester would be skipped, while the normal sync barrier would update
trunk and allow the queue to continue with the upstack branches.

I’d cover the external-merge path, upstack continuation, and the
closed-without-merge case in tests.

Does that direction sound right? If so, I’d be happy to take this issue.

[abhinav]

Hello! Yes, a change would be welcome. Otherwise I'll try to get to this soon (maybe this weekend).
You're right, it's likely just a matter of checking if the change is already merged during the poll loop.

My first thought was that ChangeMergeability should report whether the change is already merged, but that would mean this protection doesn't work when a custom ready.command is used (unreleased). I think the best place for this check might be in the awaitMergeability loop here.
But yeah, if we know the change is merged, skip the merge requester, continue running sync, etc.

[chagas42]

Thanks! I’ll take a look at this.

Checking the change status inside awaitMergeability makes sense, especially to keep it working with a custom ready.command.

I’ll add coverage for the external merge case and make sure the queue skips the merge request, syncs normally, and continues with the upstack changes. I’ll open a PR once it’s ready.