nixpkgs

Issue description

I think it would be very useful to have an option to set aliases independent of a specific shell, similar to how environment.shellAliases in nixos works for all shells (bash, zsh, fish), so modules can set aliases without having to know if they should use programs.bash.shellAliases, programs.zsh.shellAliases, or programs.fish.shellAliases.

Not sure where to best

Once bazelbuild/bazel@c42a457 hits a current release. Though we have to test whether this is backward-compatible with older bazel versions we’d like to support.

Plus there might be need for skydoc support.

It would be convenient if we could ship some bash, zsh, and fish shell completions for the cargo2nix code generation tool. We could maintain these shell completions ourselves, or ideally, we could switch to clap and/or structopt for argument parsing and generate these completions at build-time with a build.rs.