anchor.diff:  
     flycheck = melpaBuild rec {
       pname   = "flycheck";
  -    version = "0.23";
  +    version = "0.25.1";
       src = fetchFromGitHub {
         owner  = pname;
         repo   = pname;
         rev    = version;
  -      sha256 = "1ydk1wa7h7z9qw7prfvszxrmy2dyzsdij3xdy10rq197xnrw94wz";
  -    };
  -    packageRequires = [ dash let-alist pkg-info ];
  +      sha256 = "19mnx2zm71qrf7qf3mk5kriv5vgq0nl67lj029n63wqd8jcjb5fi";
  +    };
  +    packageRequires = [ dash let-alist pkg-info seq ];
       meta = {
         description = "On-the-fly syntax checking, intended as replacement for the older Flymake which is part of Emacs";
         license = gpl3Plus;
  
positive.code: 
    tracking = melpaBuild rec {
      pname   = "tracking";
      version = "1.5";
      src = fetchFromGitHub {
        owner  = "jorgenschaefer";
        repo   = "circe";
        rev    = "v${version}";
        sha256 = "08dsv1dzgb9jx076ia7xbpyjpaxn1w87h6rzlb349spaydq7ih24";
      };
      packageRequires = [ shorten ];
      fileSpecs = [ "lisp/tracking*.el" ];
      meta = {
        description = "Register buffers for user review library for Emacs";
        license = gpl3Plus;
  
negative.code: 
    lui = melpaBuild rec {
      pname   = "lui";
      version = circe.version;
      src     = circe.src;
      packageRequires = [ tracking ];
      fileSpecs = [ "lui*.el" ];
      meta = {
        description = "User interface library for Emacs";
        license = gpl3Plus;
  