I don't get why I'm marked as author in commits for two last PRs that I merged. I have done everything as usual (i.e. clicking on the merge commit button). Either it's a Github bug or they are changing something. We'll see what happens for other PRs merged today.

FYI, we are also seeing this problem in some of our repos. The merging author does seems to be a github problem.

We just sent a bug report to the github support. Perhaps all related project should do so to escalate the issue.

Thanks for the confirmation! I also contacted Github support. This seem related to https://github.community/t5/How-to-use-Git-and-GitHub/Authorship-of-merge-commits-made-by-Github-Apps-changed/m-p/48797#.

Response from Github suport:

Thanks for writing in about this!

This is an intentional change that our team recently deployed and I'm sorry to hear that's causing trouble.When a user chooses to squash and merge a PR they are taking authorship of the commit. If they were merging the PR and creating a merge commit that merge commit would be attributed to them as author, so we wanted to be consistent with that hence the change. We are also aware that we should be setting the author as a co-author and we can see that's not happening every time.

We've passed this on to our team both as feedback about the recent changes and to look into why co-authors are not being set as expected.
[..]

It's possible that I had removed the Co-authored-by tag by accident in this case.

@scikit-learn/core-devs FYI, when you next merge PR please make sure you keep Co-authored-by tag in the commit description for the PR author.

FYI, this issue (the change in commit author) got escalated to me at GitHub. We have a bug in our squash and merge logic right now (introduced yesterday) which causes the original PR author to be removed from the list of commit co-authors in some cases. We're working on a fix now.

(The change to make the merger an author will persist, as that is what git merge --squash uses, but the loss of the co-authored-by in the auto-generated commit message is a bug - sorry about that!)

Thanks @greysteil for working on this. Is it possible to give an option to retain the old behavior?

Personally I feel that the old squash merge behavior is better. The new way gives additional stats to the merger and can be confusing when looking into the commit history of maintainers.

We could go with the rebase merge. But one thing that we really liked about the original squash merge is that it directly generates commit messages that links to the PR.

Would love to see if there is a way for community to choose the behavior they want

Thanks for the feedback - we're going to revert the default behaviour back to the previous, PR-creator-as-author, setup. The fix will go out in the next 24 hours and we'll think of another way to address the problems the change was intended to solve.

Good to hear this is being rolled back. However, there is a point that I haven't seen come up in this discussion which I think is important. Keeping exact records of authorship information in the commit is really important. I feel that merging that with co-authorship is not entirely being accurate as not every contributor has commit rights in the github projects and different projects have different maintainer structures. It is important to keep accurate records of authorship as projects need to be aware of who authored what, so why is this needed ? This is needed in case there is a requirement for relicensing or any other query regarding the authorship and yes that does happen in a long running project that uses git as a version control system and github as a hosting system.

My 2 cents.

Thanks,
Ramana