s-s-d: Print valid values for IO scheduler class in --help output

debian/changelog

@@ -93,6 +93,8 @@ dpkg (1.15.1) UNRELEASED; urgency=low
   * Preserve faulting errno when printing reason in start-stop-daemon fatal
     function.
   * Only print fatal errno string in start-stop-daemon if it was non-zero.
+  * Print the valid values for the IO scheduler class in start-stop-daemon
+    --help output.
 
   [ Frank Lichtenheld ]
   * Dpkg::Version: Remove unnecessary function next_elem which just

utils/start-stop-daemon.c

@@ -391,6 +391,9 @@ do_help(void)
 "The process scheduler <policy> can be one of:\n"
 "  other, fifo or rr\n"
 "\n"
+"The IO scheduler <class> can be one of:\n"
+"  real-time, best-effort or idle\n"
+"\n"
 "Exit status:  0 = done      1 = nothing done (=> 0 if --oknodo)\n"
 "              3 = trouble   2 = with --retry, processes wouldn't die\n");
 }