anchor.diff:  # TODO: build release tarballs, repo vendors pdfs
   
   let
  -  version = "2019-03-01";
  +  date = "2019-03-01";
   in
   stdenv.mkDerivation rec {
  -  name = "opengl-headers-${version}";
  +  name = "opengl-headers-${date}";
   
     src = fetchurl {
  -    name = "opengl-headers-${version}.tar.xz";
  -    multihash = "QmZdRTzsSxGWTSzmChywUgo6drKFoho8qDh4FagumAM3eS";
  -    sha256 = "7cfa0ed4091b4d04c33b1be3c30361f9613b7301744f0b4b6397b923d82295d0";
  +    name = "opengl-headers-${date}.tar.xz";
  +    multihash = "QmdguDdKPiByjdNGu5bCpsoPcHyrTXq5UoycS3hrpZMtNX";
  +    sha256 = "64a86c8157ebb9fcdc3adaf563d28e65ad6b0b85b9a609fad0890b5c61ccb423";
     };
   
     configurePhase = ":";
  
positive.code:       postPatch = ''
          sed -i xml/genglvnd.py \
            -e 's,drafts/,,'
        '';
  
        configurePhase = ":";
  
negative.code:             api/xml/"$(basename "$xml")"
          done
  
          tar -Jcvf opengl-headers-${date}.tar.xz api/
        '';
  
        installPhase = ''
          install -D -m644 -v 'opengl-headers-${date}.tar.xz' \
            "$out/opengl-headers-${date}.tar.xz"
        '';
      };
    };
  