anchor.diff:      gc = {
         automatic = true;
         dates = "10:00";
  -      options = "--delete-older-than 14";
  +      options = "--delete-older-than 30";
       };
   
       trustedBinaryCaches = [ https://cache.nixos.org https://hydra.nixos.org ];
  
positive.code:     binaryCaches = [ https://cache.nixos.org https://hydra.nixos.org ];
      binaryCachePublicKeys = [ "hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=" ];
  
      extraOptions = ''
        auto-optimise-store = true
      '';
  
negative.code:   };
  
    environment.systemPackages = with pkgs; [
      ( lib.overrideDerivation atom (attrs: {
        name = "atom-1.6.2";
        src = fetchurl {
          url = "https://github.com/atom/atom/releases/download/v1.6.2/atom-amd64.deb";
          sha256 = "1kl2pc0smacn4lgk5wwlaiw03rm8b0763vaisgp843p35zzsbc9n";
          name = "atom-1.6.2.deb";
        };
      }))
      binutils
      emacs
      gitFull
  