anchor.diff:    src = fetchFromGitHub {
       owner = "NixOS";
       repo = "systemd";
  -    rev = "31859ddd35fc3fa82a583744caa836d356c31d7f";
  -    sha256 = "1xci0491j95vdjgs397n618zii3sgwnvanirkblqqw6bcvcjvir1";
  +    rev = "nixos-v${version}";
  +    sha256 = "1m9mhv7b4kfa43z79106gpgxx51zlhvvfjrlmimdsvsiw72nzldj";
     };
   
     prePatch = let
  
positive.code:   pythonLxmlEnv = buildPackages.python3Packages.python.withPackages ( ps: with ps; [ python3Packages.lxml ]);
  
  in stdenv.mkDerivation rec {
    version = "239";
    name = "systemd-${version}";
  
    # When updating, use https://github.com/systemd/systemd-stable tree, not the development one!
  
negative.code:         # When the URL disappears, it typically means that Debian has new patches
          # (probably security) and updating to new tarball will apply them as well.
          name = "systemd-debian-patches.tar.xz";
          url = mirror://debian/pool/main/s/systemd/systemd_239-12~bpo9+1.debian.tar.xz;
          sha256 = "0v9f62gyfiw5icdrdlcvjcipsqrsm49w6n8bqp9nb8s2ih6rsfhg";
        };
        # Note that we skip debian-specific patches, i.e. ./debian/patches/debian/*
      in ''
  