anchor.diff: -{ stdenv, fetchurl, pythonPackages, file, less
  +{ stdenv, fetchFromGitHub, pythonPackages, file, less
   , imagePreviewSupport ? true, w3m ? null}:
   
   with stdenv.lib;
  
positive.code: assert imagePreviewSupport -> w3m != null;
  
  pythonPackages.buildPythonApplication rec {
    name = "ranger-1.8.1";
  
    meta = {
      description = "File manager with minimalistic curses interface";
      homepage = http://ranger.nongnu.org/;
      license = stdenv.lib.licenses.gpl3;
      platforms = stdenv.lib.platforms.unix;
    };
  
    src = fetchurl {
      url = "http://ranger.nongnu.org/${name}.tar.gz";
      sha256 = "1d11qw0mr9aj22a7nhr6p2c3yzf359xbffmjsjblq44bjpwzjcql";
    };
  
    checkInputs = with pythonPackages; [ pytest ];
  
negative.code:       --replace "set preview_images false" "set preview_images true" \
    '';
  
    meta =  with stdenv.lib; {
      description = "File manager with minimalistic curses interface";
      homepage = http://ranger.github.io/;
      license = licenses.gpl3;
      platforms = platforms.unix;
      maintainers = [ maintainers.magnetophon ];
    };
  }
  