anchor.diff:  , python3Packages
   }:
   
  -# We build our own dist tarballs, upstream repo vendors pdfs.
  +# NOTE: We build our own dist tarballs, upstream repo vendors pdfs.
   
   let
  -  date = "2019-03-01";
  +  date = "2019-05-29";
   in
   stdenv.mkDerivation rec {
     name = "opengl-headers-${date}";
   
     src = fetchurl {
       name = "opengl-headers-${date}.tar.xz";
  -    multihash = "QmauGzZP6Sk8sef8HytfW9Xik83R6M9UNkAMQ9cmUuL8Ye";
  -    sha256 = "1d2904278c9670cb1a7720a599761159c583057d2105dcae1408c6eea51ed228";
  +    multihash = "QmdG7GAVruk97ZbAaADvEGd1QS1BSzQS1tvmVVsEFPQLLJ";
  +    sha256 = "d1b5979a28636014dcb7571c8fb3a375e65e9d187b0d6b038691dc345a53c705";
     };
   
     configurePhase = ":";
  
positive.code:         version = 6;
          owner = "KhronosGroup";
          repo = "OpenGL-Registry";
          rev = "68dba34a93b67d626b1c8b7294e4562bdaf4c996";
          sha256 = "6046f2eef181fe96379d23938de26e32621a59061d384b946db7e969bf16e99a";
        };
  
        nativeBuildInputs = [
  
negative.code:         tar -Jcvf opengl-headers-${date}.tar.xz api/
  
          install -D -m644 -v 'opengl-headers-${date}.tar.xz' \
            "$out"/opengl-headers-${date}.tar.xz
        '';
      };
    };
  