remote: run "remote rm" argv through parse_options()

The "git remote rm" command's option parsing is fairly primitive: it insists on a single argument, which it treats as the remote name, and displays a usage message otherwise. This is OK, and maybe even convenient, as you could run: git remote rm --foo to drop a remote named "--foo". But it's also weirdly unlike most of the rest of Git, which would complain that there is no option "--foo". The right way to spell it by our conventions is: git remote rm -- --foo but this doesn't currently work. So let's bring the command in line with the rest of Git (including its sibling subcommands!) by feeding argv to parse_options(). We already have an empty options array for the usage helper. Note that we have to adjust the argc index down by one, as parse_options() eats the program name from the start of the array. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>