xC: add a trivial /relay command

For there is otherwise no way of getting that information.

xC.c

@@ -12054,6 +12054,23 @@ handle_command_plugin (struct handler_args *a)
 	return true;
 }
 
+static bool
+handle_command_relay (struct handler_args *a)
+{
+	if (*a->arguments)
+		return false;
+
+	int len = 0;
+	LIST_FOR_EACH (struct client, c, a->ctx->clients)
+		len++;
+
+	if (a->ctx->relay_fd == -1)
+		log_global_status (a->ctx, "The relay is not enabled");
+	else
+		log_global_status (a->ctx, "The relay has #d clients", len);
+	return true;
+}
+
 static bool
 show_aliases_list (struct app_context *ctx)
 {
@@ -12790,6 +12807,9 @@ g_command_handlers[] =
 	{ "plugin",     "Manage plugins",
 	  "list | load <name> | unload <name>",
 	  handle_command_plugin,     0 },
+	{ "relay",      "Show relay information",
+	  NULL,
+	  handle_command_relay,      0 },
 
 	{ "alias",      "List or set aliases",
 	  "[<name> <definition>]",