Update GitHub workflows for rt pull requests

[lsf37]

GitHub Actions has changed its behaviour in how it processes pull_request_target PRs to a branch: it now seems to always run the contents of the workflow file from the master branch instead of the target branch. It says otherwise in the GUI when you display the workflow file it claims to run, but it's clearly not what is happening since that workflow file does not even contain the jobs that are being started.

The following seems to fix it:

• add a separate workflow file to master that has content for the rt branch and an explicit branch filter for just rt
• explicitly filter rt out from the triggers of the standard proof PR
• add these change sets also to the rt branch for consistency

This does mean that rt proof checks will run only for PRs to the rt branch, not to branches that themselves branch off the rt branch (e.g. when you stack pull requests), because the branch names need to be listed in the trigger filters.

We could think a of a naming scheme for branches that do trigger rt tests. Maybe rt and rt-*?

[Xaphiosis]

Is there any corresponding github bug report? Any chance they'll fix it?

Also, is it worth having any kind of manual tag / trigger phrase for those stacked PRs?

[corlewis]

Very annoying that we have to do this.

And yeah, triggering on a naming scheme or a tag would be nice.

[lsf37]

Is there any corresponding github bug report? Any chance they'll fix it?

I have not found anything. But looking at the status page of GitHub is just horrific in its own right: https://www.githubstatus.com/history -- 19 incidents in February alone and that all just in the first 10 days of Feb.

Also, is it worth having any kind of manual tag / trigger phrase for those stacked PRs?

There is already a manual trigger for both workflow files, so in theory that part should work.