anchor.diff:          version = 6;
           owner = "KhronosGroup";
           repo = "OpenGL-Registry";
  -        rev = "68dba34a93b67d626b1c8b7294e4562bdaf4c996";
  -        sha256 = "6046f2eef181fe96379d23938de26e32621a59061d384b946db7e969bf16e99a";
  +        rev = "696ac22968a6fc1c8ec11cbe8582505a38df0521";
  +        sha256 = "97f8dee46b8318f63f45f8518551dc201bbdaf93c6d51d1a332be1193b5dd61b";
         };
   
         nativeBuildInputs = [
  
positive.code: , python3Packages
  }:
  
  # We build our own dist tarballs, upstream 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 = "QmauGzZP6Sk8sef8HytfW9Xik83R6M9UNkAMQ9cmUuL8Ye";
      sha256 = "1d2904278c9670cb1a7720a599761159c583057d2105dcae1408c6eea51ed228";
    };
  
    configurePhase = ":";
  
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
        '';
      };
    };
  