I just tested, and it does not: after merging https://github.com/ZN3val/testrepo/pull/1, https://github.com/progval/testrepo/pull/2 is not updated.
Re:Nobody Cares About Your Git History
by akoboldfrying on Saturday January 27, 2024 @04:59AM
(#39154184)
Thanks for checking, it seems I was wrong about when GitHub performs the auto-update. It happens not when the PR is merged, but rather when its underlying branch is deleted. From https://docs.github.com/en/pull-requests/collaborating-with-...:
>Note: If you delete a head branch after its pull request has been merged, GitHub checks for any open pull requests in the same repository that specify the deleted branch as their base branch. GitHub automatically updates any such pull requests, changing their base branch to the merged pull request's base branch.
(This makes more sense, since if you keep the original branch around, it must be because you want to do more with it.)
So try deleting the branch underlying your PR #1. I think #2's target should then auto-update.
It auto-closed PR #2 and did not open a new one. Also, interestingly, there was no button on PR #1 to delete the branch from there as usual, I had to go to https://github.com/progval/testrepo/branches
Assuming that's the case, you want to make #2 a local PR anyway -- that is, its source is you/bar and its target is you/foo. Once #1 gets merged to them/main (by someone with the access to the upstream repo, "them"), #2 will (I predict, based on reasons I've already given) automatically become a PR "in" the repo them. That is, its target branch will automatically change to them/main.