anchor.diff:    src = fetchFromGitHub {
       owner = "NixOS";
       repo = "systemd";
  -    rev = "31859ddd35fc3fa82a583744caa836d356c31d7f";
  -    sha256 = "1xci0491j95vdjgs397n618zii3sgwnvanirkblqqw6bcvcjvir1";
  +    rev = "nixos-v${version}";
  +    sha256 = "1rzl0iqrpa4ajvama5k3cb3yc7893c55kzcxkl3cyavpdzsw5505";
     };
   
     outputs = [ "out" "lib" "man" "dev" ];
  
positive.code:     "-Dsulogin-path=${utillinux}/bin/sulogin"
      "-Dmount-path=${utillinux}/bin/mount"
      "-Dumount-path=${utillinux}/bin/umount"
    ];
  
    preConfigure = ''
  
negative.code:   pythonLxmlEnv = buildPackages.python3Packages.python.withPackages ( ps: with ps; [ python3Packages.lxml ]);
  
  in stdenv.mkDerivation rec {
    version = "239.20181031";
    name = "systemd-${version}";
  
    # When updating, use https://github.com/systemd/systemd-stable tree, not the development one!
  