@alexanderwatanabe thanks a lot for caring about the CUDA integration here! However, I'm afraid you misunderstood the contribution process for nixpkgs. Let me try to clarify a few things:

• it's fine to file a PR against master. This is where all the development happens and the nixos-unstable-channel is created from our master. Every "new" change should somehow land on master before appearing on stable branches.
• you should avoid though to push the changes to your fork's master, instead it's better to create a feature-branch from your master-branch for the following reasons:
  • if the branch name is a bit more descriptive it makes the merge-commit more descriptive as well
  • a lot of people have further customizations on their master or somehow rely on their fork's master which can be a problem if a maintainer pushes minor fixes to a contributor's master before merging a PR.
• In case you want to backport your changes, please don't file your PR against nixos-20.03, but against release-20.03 instead. The nixos-* branches are created automatically for our channels. You can read more about this on https://howoldis.herokuapp.com/

Does this help you? If not, feel free to ping me either here or in the IRC :)