anchor.diff:              cat > "${cfg.dataDir}/buildkite-agent.cfg" <<EOF
               token="$(cat ${toString cfg.tokenPath})"
               name="${cfg.name}"
  -            meta-data="${cfg.meta-data}"
  +            ${metaData}
               build-path="${cfg.dataDir}/builds"
               hooks-path="${cfg.hooksPath}"
               ${cfg.extraConfig}
  
positive.code:           '';
  
          serviceConfig =
            { ExecStart = "${pkgs.buildkite-agent}/bin/buildkite-agent start --config /var/lib/buildkite-agent/buildkite-agent.cfg";
              User = "buildkite-agent";
              RestartSec = 5;
              Restart = "on-failure";
  
negative.code:         ##     don't end up in the Nix store.
          preStart = let
            sshDir = "${cfg.dataDir}/.ssh";
            metaData = if cfg.meta-data == ""
              then ""
              else "meta-data=${cfg.meta-data}";
          in
            ''
              mkdir -m 0700 -p "${sshDir}"
  