anchor.diff:          use-substitutes = ${if cfg.useSubstitutes then "1" else "0"}
         '';
   
  -    environment.systemPackages = [ cfg.package ];
  +    environment.systemPackages = [ hydra-package ];
   
       environment.variables = hydraEnv;
   
  
positive.code:       { wantedBy = [ "multi-user.target" ];
          requires = [ "hydra-init.service" ];
          after = [ "hydra-init.service" "network.target" ];
          path = [ cfg.package pkgs.nettools pkgs.openssh pkgs.bzip2 config.nix.package ];
          restartTriggers = [ hydraConf ];
          environment = env // {
            PGPASSFILE = "${baseDir}/pgpass-queue-runner"; # grrr
            IN_SYSTEMD = "1"; # to get log severity levels
          };
          serviceConfig =
            { ExecStart = "@${cfg.package}/bin/hydra-queue-runner hydra-queue-runner -v";
              ExecStopPost = "${cfg.package}/bin/hydra-queue-runner --unlock";
              User = "hydra-queue-runner";
              Restart = "always";
  
  
negative.code:       { wantedBy = [ "multi-user.target" ];
          requires = [ "hydra-init.service" ];
          after = [ "hydra-init.service" "network.target" ];
          path = with pkgs; [ hydra-package nettools jq ];
          restartTriggers = [ hydraConf ];
          environment = env;
          serviceConfig =
            { ExecStart = "@${hydra-package}/bin/hydra-evaluator hydra-evaluator";
              User = "hydra";
              Restart = "always";
              WorkingDirectory = baseDir;
  