anchor.diff:  
     passthru = {
       generateDistTarball = stdenv.mkDerivation rec {
  -      name = "opengl-headers-${version}";
  +      name = "opengl-headers-${date}";
   
         src = fetchFromGitHub {
           version = 6;
  
positive.code:             api/xml/"$(basename "$xml")"
          done
  
          tar -Jcvf opengl-headers-${version}.tar.xz api/
        '';
  
        installPhase = ''
          install -D -m644 -v 'opengl-headers-${version}.tar.xz' \
            "$out/opengl-headers-${version}.tar.xz"
        '';
      };
    };
  
negative.code: # TODO: build release tarballs, repo vendors pdfs
  
  let
    date = "2019-03-01";
  in
  stdenv.mkDerivation rec {
    name = "opengl-headers-${date}";
  
    src = fetchurl {
      name = "opengl-headers-${date}.tar.xz";
      multihash = "QmdguDdKPiByjdNGu5bCpsoPcHyrTXq5UoycS3hrpZMtNX";
      sha256 = "64a86c8157ebb9fcdc3adaf563d28e65ad6b0b85b9a609fad0890b5c61ccb423";
    };
  
    configurePhase = ":";
  