archive: allow --exec and --remote without equal sign

archive: allow --exec and --remote without equal sign

Convert git archive to parse_options().  The parameters --remote and --exec
are still handled by their special parser.  Define them anyway in order for
them to show up in the usage notice.

Note: in a command like "git archive --prefix --remote=a/ HEAD", the string
"--remote=a/" will be interpreted as a remote option, not a prefix, because
that special parser sees it first.  If one needs such a strange prefix, it
needs to be specified like this: "git archive --prefix=--remote=a/ HEAD"
(with an equal sign).

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>