Description
The 1.45.1 release is primarily being made because of the accidental omission of a rustfmt backport from the 1.45 beta branch after it landed in 1.44.1.
The release team discussed this today, and we'd like to implement some automation to try and prevent this in the future at relatively low cost.
The plan is to only allow landing commits in beta / stable branches if git cherry (or similar, but that seems like the right thing) indicates they've already landed in the preceding branches (beta and master for stable, just master for beta). We will also want an explicit set of commits that are just allowed.
This will slightly increase the work needed during beta backports, as this list will need updating if there are any merge conflicts at least -- but since backports are rare and usually rollups, this shouldn't be much of a problem hopefully.
We would be interested in seeing someone implement this functionality!