anchor.diff:  { stdenv, fetchFromGitHub, fetchurl, makeWrapper
  -, perl, pandoc, pythonPackages, git
  +, perl, pandoc, python2Packages, git
   , par2cmdline ? null, par2Support ? false
   }:
   
  
positive.code:     wrapProgram $out/bin/bup \
        --prefix PATH : ${git}/bin \
        --prefix PYTHONPATH : ${concatStringsSep ":" (map (x: "$(toPythonPath ${x})")
          (with pythonPackages;
           [ setuptools tornado ]
           ++ stdenv.lib.optionals (!stdenv.isDarwin) [ pyxattr pylibacl fuse ]))}
    '';
  
negative.code:     sha256 = "1hsxzrjvqa3pd74vmz8agiiwynrzynp1i726h0fzdsakc4adya4l";
    };
  
    buildInputs = [ git python2Packages.python ];
    nativeBuildInputs = [ pandoc perl makeWrapper ];
  
    postPatch = ''
  