ls-remote: use parse-options api

ls-remote: use parse-options api

Currently ls-remote uses a hand rolled parser for its command line
arguments.  Use the parse-options api instead of the hand rolled parser
to simplify the code and make it easier to add new arguments.  In
addition this improves the help message.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>