anchor.diff:  let
     quassel = pkgs.quasselDaemon;
     cfg = config.services.quassel;
  +  user = if cfg.user != null then cfg.user else "quassel";
   in
   
   {
  
positive.code: 
    config = mkIf cfg.enable {
  
      users.extraUsers = singleton
        { name = cfg.user;
          description = "Quassel IRC client daemon";
        };
      
  
      jobs.quassel =
  
negative.code: 
          preStart = ''
              mkdir -p ${cfg.dataDir}
              chown ${user} ${cfg.dataDir}
          '';
  
          exec = ''
              ${pkgs.su}/bin/su -s ${pkgs.stdenv.shell} ${user} \
                  -c '${quassel}/bin/quasselcore --listen=${cfg.interface}\
                      --port=${toString cfg.portNumber} --configdir=${cfg.dataDir}'
          '';
  