Github's conflict resolution creates merge commits that are then flagged by rustbot

This repo is probably misconfigured: merge commits probably are allowed in the repo's settings.

Recently I submitted this PR: https://github.com/rust-lang/rust/pull/136471/ . Github shows me so-called "new PR merge experience" ( https://github.com/orgs/community/discussions/143787 ). At some point Github detected a conflict between my branch and mainline and showed me a message about this. Github interface offered me to fix this conflict directly in Github interface. I agreed and fixed (in Github web interface). But then immediately @rustbot said me that merges are not allowed. So I have to remove my merge commit and do rebase instead on my computer locally.

So, for unknown reasons Github offers a user to create merge commit, despite they are not allowed. This is probably repo misconfiguration. If there is no misconfiguration, then this is a bug in Github's "new PR merge experience" and should be reported to https://github.com/orgs/community/discussions/143787 .

I consider this a high-priority bug, because it presents a major contribution roadblock. This will definitely scary away potential contributors. Think about this: at first you are asked to do a merge, but then immediately @rustbot says to you that you did something wrong and should undo. I think many potential contributor will simply think: "I don't want to contribute at all".

@rustbot label T-infra A-contributor-roadblock

Use PR 136471 and the repository's GitHub settings as starting points; compare the merge option GitHub presented with rustbot's merge-policy check. Determine whether this is repository misconfiguration or a GitHub "new PR merge experience" bug, then document the finding or report it in the linked GitHub Community discussion.