anchor.diff:    buildPhase = ":";
   
     installPhase = ''
  -    for api in api/GL{,ES{,2,3},SC{,2}}; do
  +    for api in GL{,ES{,2,3},SC{,2}}; do
         pushd $api
           while read header; do
             install -D -m644 -v $header $out/include/$(basename "$api")/$header
  
positive.code: stdenv.mkDerivation rec {
    name = "opengl-headers-${version}";
  
    src = fetchFromGitHub {
      version = 3;
      owner = "KhronosGroup";
      repo = "OpenGL-Registry";
      rev = "93e0595941ea275b95ba115e1f400283c652004d";
      sha256 = "40b8204a8c97e95913c31d11dc58527780e866424c5dd577f9a8ee2209612209";
    };
  
    configurePhase = ":";
  
negative.code: { stdenv
  , fetchurl
  , fetchFromGitHub
  , lib
  }:
  