This repo can be cleaned-up

[Anton-Latukha]

Upstream discussion is: haskell-nix/hnix#328

The split initially would probably be internal.
And even the split into separate repos essentially is a ready repo branching-out into a completely new repository with preservation of the essential part of the history, as in: https://github.com/Anton-Latukha/haskell-with-nixpkgs/graphs/contributors.