anchor.diff:  
     swiper = melpaBuild rec {
       pname   = "swiper";
  -    version = "0.6.0";
  +    version = "0.7.0";
       src = fetchFromGitHub {
         owner  = "abo-abo";
         repo   = pname;
         rev    = version;
  -      sha256 = "18madh4hvrk8sxrll84ry13n1l3ad1gnp3prj828sszrbbdp20ly";
  +      sha256 = "1kahl3h18vsjkbqvd84fb2w45s4srsiydn6jiv49vvg1yaxzxcbm";
       };
       fileSpecs = [ "swiper.el" "ivy.el" "colir.el" "counsel.el" ];
       meta = {
  
positive.code:     };
    };
  
    hi2 = melpaBuild rec {
      pname   = "hi2";
      version = "1.0";
  
negative.code: 
    projectile = melpaBuild rec {
      pname   = "projectile";
      version = "0.13.0";
      src = fetchFromGitHub {
        owner  = "bbatsov";
        repo   = pname;
        rev    = "v${version}";
        sha256 = "1rl6n6v9f4m7m969frx8b51a4lzfix2bxx6rfcfbh6kzhc00qnxf";
      };
      fileSpecs = [ "projectile.el" ];
      packageRequires = [ dash helm pkg-info ];
  