anchor.diff:  }:
   
   let
  -  version = "2019-02-13";
  +  date = "2019-02-13";
   in
   stdenv.mkDerivation rec {
  -  name = "egl-headers-${version}";
  +  name = "egl-headers-${date}";
   
     src = fetchurl {
       url = "http://egl-registry.tar.xz";
  -    multihash = "Qmf3CaunyCXXiyyd6fypvYZv6Q8cDU28ZnJkLqauH26Wxn";
  -    sha256 = "263cd3090ab76adc3fba3e8e97ba54b44e1109c8e15dfca99851c255319b0f9b";
  +    multihash = "Qma9rtynxUNEy8AxSsuEE7kCNqYvMU8bTeJQL8CiYo27TU";
  +    sha256 = "de926279c49b99d2d702217a073cf25b60d58cb81a30a91150cc0892b2b32532";
     };
   
     configurePhase = ":";
  
positive.code: 
    passthru = {
      generateDistTarball = stdenv.mkDerivation rec {
        name = "egl-headers-dist-${version}";
  
        src = fetchFromGitHub {
          version = 6;
  
negative.code:           install -D -m644 -v "$xml" ${name}/xml/"$(basename "$xml")"
          done
  
          tar -Jcvf opengl-headers-${date}.tar.xz ${name}/
  
          install -D -m644 -v 'opengl-headers-${date}.tar.xz' \
            "$out/egl-headers-${date}.tar.xz"
        '';
      };
    };
  