anchor.diff:  
     exp = buildFromGitHub {
       version = 3;
  -    rev = "be09b602c40b1028d91bf805b38a6f54741fc34d";
  +    rev = "6e195c1fee8bc55fa0e208cf08a468b39be428e0";
       owner = "golang";
       repo = "exp";
  -    sha256 = "0kjd832vzds23as8ffkd0qq5i62nwm0f8s4fimijxgjg3w4c8gfd";
  -    date = "2017-09-29";
  +    sha256 = "1cr00dnyn7xbv0hyrlkncwiipnv6whs1j4s7q2qg7jb83gia8pva";
  +    date = "2017-11-17";
       goPackagePath = "golang.org/x/exp";
       subPackages = [
         "ebnf"
  
positive.code: 
    ugorji_go = buildFromGitHub {
      version = 3;
      date = "2017-11-14";
      rev = "649a5588a82cf604df7624361b11532a7b72a4a7";
      owner = "ugorji";
      repo = "go";
      sha256 = "0zzx08ln7k4iiaas2rvsrz5mg0zb685fanl2iac94ahb96zvn8ba";
      goPackageAliases = [
        "github.com/hashicorp/go-msgpack"
      ];
  
negative.code: 
    rollinghash = buildFromGitHub {
      version = 3;
      rev = "5a57de9164293f767ac4f91423aa927c7b996098";
      owner  = "chmduquesne";
      repo   = "rollinghash";
      sha256 = "0yhl2p82gkkslxx668d4qlf5gi98yknp5g4vggpws86vsbp8djlz";
      date = "2017-11-19";
      propagatedBuildInputs = [
        bytefmt
      ];
    };
  
    roundtrip = buildFromGitHub {
  