anchor.diff:  
     sys = buildFromGitHub {
       version = 5;
  -    rev = "7dca6fe1f43775aa6d1334576870ff63f978f539";
  -    date = "2018-03-08";
  +    rev = "2f1e207ee39ff70f3433e49c6eb52677a515e3b5";
  +    date = "2018-03-16";
       owner  = "golang";
       repo   = "sys";
  -    sha256 = "10rpr4lasgriazbx9i5693f821s94dh2hg4r0h81i7984bh1k3i3";
  +    sha256 = "1x9xpa7wchhs2368bx7wslz4kps5fvknmpjsihpj6x6wkzjhd7pk";
       goPackagePath = "golang.org/x/sys";
     };
   
  
positive.code:     version = 5;
      owner = "elves";
      repo = "elvish";
      rev = "3d4bb53dfc300d57c2c5a16c76191765ffc6b889";
      sha256 = "0fnmn8cavv4qr6d1fi5gpnisrh1990r206mwgyjy4gnk59w2092y";
      propagatedBuildInputs = [
        bolt
        go-isatty
  
negative.code:       sys
      ];
      meta.useUnstable = true;
      date = "2018-03-16";
    };
  
    eme = buildFromGitHub {
  