[CIR][Github][CI] Add clangir upstream rebase workflow

[xlauko]

No description provided.

[xlauko]

@lanza I believe this does the job. To be secure at the moment it just creates rebased-main without push to main.

[xlauko]

It needs to be triggered manually at the moment. I think we can let it run every night then?

Before that, we need to setup WORKFLOW_TOKEN to have access to write to repo.

[lanza]

It needs to be triggered manually at the moment. I think we can let it run every night then?

Yea that makes sense IMO. I don't remember if we talked about this, but I don't think it should actualyl push every night. That would cause unnecessary churn on PRs where they are submitted on day X, we rebase on night X, and thus the PRs broken by the time they are reviewed on day X+1.

Before that, we need to setup WORKFLOW_TOKEN to have access to write to repo.

But I have no clue how to do either of these things, never really touched github actions. Do you need extra permissions to do this or something?

Only change I can think of for the diff would to add an optional -x or something that does the --exec 'ninja -C build check-clang-cir' functionality. Then the script can be used for performing manual rebases where we need human intervention.