anchor.diff:  
       } // originalEtc // extraTrustedKeys // testRemote;
   
  -    services.dbus.packages = [ pkgs.fwupd ];
  +    services.dbus.packages = [ cfg.package ];
   
  -    services.udev.packages = [ pkgs.fwupd ];
  +    services.udev.packages = [ cfg.package ];
   
  -    systemd.packages = [ pkgs.fwupd ];
  +    systemd.packages = [ cfg.package ];
   
       systemd.tmpfiles.rules = [
         "d /var/lib/fwupd 0755 root root -"
  
positive.code:     "fwupd/remotes.d/fwupd-tests.conf" = {
        source = pkgs.runCommand "fwupd-tests-enabled.conf" {} ''
          sed "s,^Enabled=false,Enabled=true," \
          "${pkgs.fwupd.installedTests}/etc/fwupd/remotes.d/fwupd-tests.conf" > "$out"
        '';
      };
    } else {};
  
negative.code:   cfg = config.services.fwupd;
    originalEtc =
      let
        mkEtcFile = n: nameValuePair n { source = "${cfg.package}/etc/${n}"; };
      in listToAttrs (map mkEtcFile cfg.package.filesInstalledToEtc);
    extraTrustedKeys =
      let
        mkName = p: "pki/fwupd/${baseNameOf (toString p)}";
  