Topstack PR "merged" via API / third-party tool

[arnaudriegert]

Working with a stack PR1 (based on main) / PR2 / PR3 (tip).

Reviewer on PR3 opens it in Graphite (our current stacking tool, which we hope to drop if the trial is successful) and accidentally clicks on Merge.

As far as Graphite is concerned, this is a regular PR whose base is PR2's branch (no branch protection rules there).

➡️ PR3 is marked as merged in GitHub whereas PR1 and PR2 are open
➡️ Thankfully, it didn't land on main... or in PR2's branch as far as I can tell
➡️ I was unable to recreate a new "PR3b" on top of PR2 — had to target main instead (which was fine in this case because it's independent)

I'd expect GH to prevent PR3 from being merged as a standalone PR via the API in this scenario (GitHub UI doesn't allow it).