anchor.diff:  { stdenv, lib, fetchhg, cmake, which, python3, osi, cplex }:
   
   stdenv.mkDerivation {
  -  name = "fast-downward-2019-05-13";
  +  version = "19.12";
  +  pname = "fast-downward";
   
     src = fetchhg {
       url = "http://hg.fast-downward.org/";
  -    rev = "090f5df5d84a";
  -    sha256 = "14pcjz0jfzx5269axg66iq8js7lm2w3cnqrrhhwmz833prjp945g";
  +    rev = "41688a4f16b3";
  +    sha256 = "08m4k1mkx4sz7c2ab7xh7ip6b67zxv7kl68xrvwa83xw1yigqkna";
     };
   
     nativeBuildInputs = [ cmake which ];
  
positive.code: 
    enableParallelBuilding = true;
  
    postPatch = ''
      cd src
      # Needed because the package tries to be too smart.
      export CC="$(which $CC)"
      export CXX="$(which $CXX)"
    '';
  
    installPhase = ''
      install -Dm755 bin/downward $out/libexec/fast-downward/downward
      cp -r ../translate $out/libexec/fast-downward/
      install -Dm755 ../../fast-downward.py $out/bin/fast-downward
      mkdir -p $out/${python3.sitePackages}
      cp -r ../../driver $out/${python3.sitePackages}
  
      wrapPythonProgramsIn $out/bin "$out $pythonPath"
      wrapPythonProgramsIn $out/libexec/fast-downward/translate "$out $pythonPath"
  
negative.code:       echo "Moving $i to $dest"
        mv "$i" "$dest"
      done
  
      substituteInPlace $out/${python3.sitePackages}/driver/arguments.py \
        --replace 'args.build = "release"' "args.build = \"$out/libexec/fast-downward\""
    '';
  
    meta = with stdenv.lib; {
  