Even though "git update-index" was updated to use parse-options
infrastracture some time ago to make it possible to show list of
options with usage_with_options(), "git update-index -h" only shows
the usage. Detect this case and call usage_with_options() to show
the list of options as well.
Signed-off-by: Antoine Pelisse <apelisse@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>