anchor.diff:      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;
  
positive.code:     zsh = callPackage ./zsh {
        site-functions = builtins.map
          (p: "${p}/share/zsh/site-functions")
          [ ddgr pure-prompt hub pijul pkgs.nix-zsh-completions ];
      };
  
      # Tmux with a custom tmux.conf baked in
  
negative.code:       pkgs.gawk
        pkgs.gnupg
        hub
        lab
        pkgs.less
        pkgs.nix
        pkgs.nix-zsh-completions
  