anchor.diff:      zsh = callPackage ./zsh {
         site-functions = builtins.map
           (p: "${p}/share/zsh/site-functions")
  -        [ ddgr pure-prompt hub pijul pkgs.nix-zsh-completions ];
  +        [ ddgr pure-prompt hub lab pijul pkgs.nix-zsh-completions ];
       };
   
       # Tmux with a custom tmux.conf baked in
  
positive.code:       pkgs.gawk
        pkgs.gnupg
        hub
        pkgs.less
        pkgs.nix
        pkgs.nix-zsh-completions
  
negative.code:     sha256 = "0fvxn8w368wg8d0lgbmrkr3ws1i1484hjrzsr65y4wldz0w9chrq";
    }) {};
  
    pkgs-unstable = import (builtins.fetchTarball {
      # Descriptive name to make the store path easier to identify
      name = "nixpkgs-master-2019-05-17";
      url = "https://github.com/nixos/nixpkgs/archive/619492c03ecfc6cde541a680a1ac1e5250584acc.tar.gz";
      # hash obtained with `nix-prefetch-url --unpack <url from above>`
      sha256 = "0ylk57v97mvzh37055my8z5marfcq7ircxjlnkqgg55y5xdcqzw1";
    }) {};
  
    hub = pkgs.gitAndTools.hub;
  
    lab = pkgs-unstable.gitAndTools.lab;
  
    custom = rec {
      inherit (pkgs) callPackage;
  