anchor.diff:  { stdenv
   , lib
   , fetchFromGitHub
  +, nix-update-script
   , autoreconfHook
   , perl
   , pkg-config
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "sidplayfp";
    version = "2.1.1";
  
    src = fetchFromGitHub {
      owner = "libsidplayfp";
      repo = "sidplayfp";
      rev = "v${version}";
      sha256 = "0s3xmg3yzfqbsnlh2y46w7b5jim5zq7mshs6hx03q8wdr75cvwh4";
    };
  
    nativeBuildInputs = [ autoreconfHook perl pkg-config ];
  
negative.code: 
    enableParallelBuilding = true;
  
    passthru = {
      updateScript = nix-update-script {
        attrPath = pname;
      };
    };
  
    meta = with lib; {
      description = "A SID player using libsidplayfp";
      homepage = "https://github.com/libsidplayfp/sidplayfp";
  