Simply using a given branch doesn’t really do it. I’m seeing stuff thats too young and too old for my project.
Do I just import derivations? Do I do a nix-env -iA xxxxxx? If so, what should be working. I’ve yet to be able to nix-env -iA clang_7_1_0 (for example) and get anything useful. I’ve tried a number of variants. The funny thing is how few examples of that there are in the documentation.
Most packages I’ve seen care a lot about the versions dependent packages, and often have very specific needs.