hydra: restart daemons on config change

https://github.com/NixOS/hydra/pull/491

nixos/modules/services/continuous-integration/hydra/default.nix

@@ -308,6 +308,7 @@ in
         requires = [ "hydra-init.service" ];
         after = [ "hydra-init.service" ];
         environment = serverEnv;
+        restartTriggers = [ hydraConf ];
         serviceConfig =
           { ExecStart =
               "@${cfg.package}/bin/hydra-server hydra-server -f -h '${cfg.listenHost}' "
@@ -324,6 +325,7 @@ in
         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 = "${baseDir}/pgpass-queue-runner"; # grrr
           IN_SYSTEMD = "1"; # to get log severity levels
@@ -345,6 +347,7 @@ in
         requires = [ "hydra-init.service" ];
         after = [ "hydra-init.service" "network.target" ];
         path = with pkgs; [ cfg.package nettools jq ];
+        restartTriggers = [ hydraConf ];
         environment = env;
         serviceConfig =
           { ExecStart = "@${cfg.package}/bin/hydra-evaluator hydra-evaluator";