anchor.diff:  stdenv.mkDerivation rec {
     name = "opengl-headers-${version}";
   
  -  src = fetchFromGitHub {
  -    version = 3;
  -    owner = "KhronosGroup";
  -    repo = "OpenGL-Registry";
  -    rev = "93e0595941ea275b95ba115e1f400283c652004d";
  -    sha256 = "40b8204a8c97e95913c31d11dc58527780e866424c5dd577f9a8ee2209612209";
  +  src = fetchurl {
  +    url = "http://opengl-headers.tar.xz";
  +    multihash = "QmZvWAAPb4FAB4psCuvfKZW1N638AFG7ZTLX1Jr4kRE8UB";
  +    sha256 = "77172528da0549cebdaf4f5f129e020bfad722fdf9808f5e32d14766c2e81081";
     };
   
     configurePhase = ":";
  
positive.code:       popd
      done
    '';
  
    meta = with lib; {
      description = "OpenGL, OpenGL ES, and OpenGL ES-SC API headers.";
  
negative.code: { stdenv
  , fetchurl
  , fetchFromGitHub
  , lib
  }:
  