display whether an option takes an argument in the usage output

src/_usage.c

@@ -9,15 +9,20 @@
 
 static void usage (int exit_status)
 {
+	const char * const has_arg[] = { "", "<arg>", "[arg]" };
 	int i;
 	printf ("Usage: " APPLET " [options] ");
 #ifdef extraopts
 	printf (extraopts);
 #endif
 	printf ("\n\nOptions: [" getoptstring "]\n");
-	for (i = 0; longopts[i].name; ++i)
-		printf ("  -%c, --%-15s %s\n", longopts[i].val, longopts[i].name,
-		        longopts_help[i]);
+	for (i = 0; longopts[i].name; ++i) {
+		int len = printf ("  -%c, --%s %s", longopts[i].val, longopts[i].name,
+		                  has_arg[longopts[i].has_arg]);
+		while (++len < 25)
+			printf (" ");
+		puts (longopts_help[i]);
+	}
 	exit (exit_status);
 }