anchor.diff:  
     maxminddb-golang = buildFromGitHub {
       version = 2;
  -    date = "2016-09-10";
  -    rev = "e528c2f39cc9d9065d7806e82ccadb7e2cd10395";
  +    date = "2016-09-19";
  +    rev = "2af0544f8e032bc7a363e897fbd9c6ed4884a1d6";
       owner  = "oschwald";
       repo   = "maxminddb-golang";
  -    sha256 = "13v8r6p81z52csgaih99x4zvyqrb0qbfzp0n5apavyccns8armj9";
  +    sha256 = "0swgb6xgkf995qvr0zk66y2m5h3p6amcb0k9j52afkvj3yxrx8am";
       propagatedBuildInputs = [
         sys
       ];
  
positive.code: 
    sys = buildFromGitHub {
      version = 2;
      rev = "30de6d19a3bd89a5f38ae4028e23aaa5582648af";
      date = "2016-09-07";
      owner  = "golang";
      repo   = "sys";
      sha256 = "1a1j8cycykcd91h22rp0bk6zjy9nln2qpxiggpjcpd3szl9k99zv";
      goPackagePath = "golang.org/x/sys";
      goPackageAliases = [
        "github.com/golang/sys"
  
negative.code: 
    go4 = buildFromGitHub {
      version = 2;
      date = "2016-09-19";
      rev = "27882e489dcd7ade28c033b82c6d498661c4dc42";
      owner = "camlistore";
      repo = "go4";
      sha256 = "1rnr69lcnkzxzlvfyl1afcrd7mnyd3zfaw1720dxhmsh14f1vhs8";
      goPackagePath = "go4.org";
      goPackageAliases = [ "github.com/camlistore/go4" ];
      buildInputs = [
  