nixos/kmscon: use upstream service file

nixos/modules/services/ttys/kmscon.nix

@@ -67,36 +67,24 @@ in {
   };
 
   config = mkIf cfg.enable {
-    # Largely copied from unit provided with kmscon source
-    systemd.units."kmsconvt@.service".text = ''
-      [Unit]
-      Description=KMS System Console on %I
-      Documentation=man:kmscon(1)
-      After=systemd-user-sessions.service
-      After=plymouth-quit-wait.service
-      After=systemd-logind.service
-      After=systemd-vconsole-setup.service
-      Requires=systemd-logind.service
-      Before=getty.target
-      Conflicts=getty@%i.service
-      OnFailure=getty@%i.service
-      IgnoreOnIsolate=yes
-      ConditionPathExists=/dev/tty0
+    systemd.packages = [ pkgs.kmscon ];
 
-      [Service]
-      ExecStart=
-      ExecStart=${pkgs.kmscon}/bin/kmscon "--vt=%I" ${cfg.extraOptions} --seats=seat0 --no-switchvt --configdir ${configDir} --login -- ${pkgs.shadow}/bin/login -p ${autologinArg}
-      UtmpIdentifier=%I
-      TTYPath=/dev/%I
-      TTYReset=yes
-      TTYVHangup=yes
-      TTYVTDisallocate=yes
+    systemd.services."kmsconvt@" = {
+      after = [ "systemd-logind.service" "systemd-vconsole-setup.service" ];
+      requires = [ "systemd-logind.service" ];
 
-      X-RestartIfChanged=false
-    '';
+      serviceConfig.ExecStart = [
+        ""
+        ''
+          ${pkgs.kmscon}/bin/kmscon "--vt=%I" ${cfg.extraOptions} --seats=seat0 --no-switchvt --configdir ${configDir} --login -- ${pkgs.shadow}/bin/login -p ${autologinArg}
+        ''
+      ];
+
+      restartIfChanged = false;
+      aliases = [ "autovt@.service" ];
+    };
 
     systemd.suppressedSystemUnits = [ "autovt@.service" ];
-    systemd.units."kmsconvt@.service".aliases = [ "autovt@.service" ];
 
     systemd.services.systemd-vconsole-setup.enable = false;
     systemd.services.reload-systemd-vconsole-setup.enable = false;