I figured I should post this to Discourse to give this some more attention.
We used to merge a lot of undetected mass-rebuilds to master. This is, because ofborg doesn’t warn if a change rebuilds all NixOS tests which imposes a notable overhead on the build infrastructure.
You’ll notice by now if your PR has the label 10.rebuild-nixos-tests.
In that case, please make sure to target staging-nixos instead. This branch will be merged along with kernel updates from now on. This happens approximately once per week.
See also nixpkgs/CONTRIBUTING.md at 4b3a7fbda14c1310e607b79caefe103cbffb1fa9 · NixOS/nixpkgs · GitHub