anchor.diff:      tig
       universal-ctags
       unrar
  +    unstable.emacs
       unzip
       usbutils
       wget
  
positive.code:     cmus
      curl
      daemonize
      emacs
      fd
      file
      fzf
  
negative.code: { pkgs, config, ... }:
  
  let
    unstable = import (builtins.fetchGit {
      name = "nixos-unstable-2019-04-29";
      url = https://github.com/nixos/nixpkgs/;
      rev = "496f9309480b22173e25885bc7c128c30fbd4da3"; # emacs 26.2
    }) {
      config = config.nixpkgs.config;
    };
  in
  
  {
    nixpkgs.config.allowUnfree = true;
  