Add --update-now: update trigger that only goes through the service's control channel

cmd/gpu-turnstile/main.go

@@ -58,7 +58,7 @@ func stdoutIsTerminal() bool {
 // --install-service / --remove-service switches, --no-copy, -h/--help,
 // -v/--version, --force-update and the hidden --elevated-child marker from
 // args.
-func parseFlags(args []string) (configPath string, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild bool, rest []string) {
+func parseFlags(args []string) (configPath string, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild bool, rest []string) {
 	rest = args[:0]
 	for i := 0; i < len(args); i++ {
 		switch {
@@ -79,13 +79,15 @@ func parseFlags(args []string) (configPath string, install, remove, noCopy, help
 			showVersion = true
 		case args[i] == "--force-update" || args[i] == "-force-update":
 			forceUpdate = true
+		case args[i] == "--update-now" || args[i] == "-update-now":
+			updateNow = true
 		case args[i] == "--elevated-child":
 			elevatedChild = true
 		default:
 			rest = append(rest, args[i])
 		}
 	}
-	return configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, rest
+	return configPath, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild, rest
 }
 
 // versionLine is printed at the top of every help and error screen.
@@ -101,6 +103,8 @@ Usage:
   gpu-turnstile --force-update                                check for a signed update now,
                                                               apply it and restart the service
                                                               (no admin needed when the service runs)
+  gpu-turnstile --update-now                                  like --force-update, but only
+                                                              through the running service
   gpu-turnstile -h | --help                                   this help
 
 Options:
@@ -131,12 +135,12 @@ func fatalUsage(format string, args ...any) {
 }
 
 func main() {
-	configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, args := parseFlags(os.Args[1:])
+	configPath, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild, args := parseFlags(os.Args[1:])
 	if showVersion {
 		fmt.Println(version)
 		return
 	}
-	bare := configPath == "" && !install && !remove && !forceUpdate && !elevatedChild && len(args) == 0
+	bare := configPath == "" && !install && !remove && !forceUpdate && !updateNow && !elevatedChild && len(args) == 0
 	if help || (bare && stdoutIsTerminal()) {
 		// Bare invocation in a terminal (e.g. double-clicked on Windows)
 		// shows the help instead of starting a proxy window with no visible
@@ -159,12 +163,16 @@ func main() {
 		fatalUsage("error: --install-service and --remove-service are mutually exclusive")
 	case forceUpdate && (install || remove):
 		fatalUsage("error: --force-update cannot be combined with --install-service/--remove-service")
+	case updateNow && (install || remove || forceUpdate):
+		fatalUsage("error: --update-now cannot be combined with other commands")
 	case install:
 		os.Exit(serviceCommand(configPath, true, noCopy, elevatedChild))
 	case remove:
 		os.Exit(serviceCommand(configPath, false, noCopy, elevatedChild))
 	case forceUpdate:
 		os.Exit(forceUpdateCommand(configPath, elevatedChild))
+	case updateNow:
+		os.Exit(updateNowCommand())
 	}
 	if len(args) > 0 {
 		fatalUsage("error: unknown arguments: %s", strings.Join(args, " "))
@@ -418,6 +426,17 @@ func printControlReply(reply string) int {
 	return 0
 }
 
+// updateNowCommand only goes through the running service's control channel
+// (no direct check, no elevation): the unprivileged update trigger.
+func updateNowCommand() int {
+	reply, err := control.Ask(control.CmdUpdateNow)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n\ngpu-turnstile: no running service to ask — use --force-update for a direct check\n", versionLine())
+		return 1
+	}
+	return printControlReply(reply)
+}
+
 // reportElevatedUpdate prints the parent's summary of an elevated
 // --force-update child: exitCodeStaged means the child staged a new binary,
 // 0 means it found nothing to do. to is the tag the parent's own check