archive: remove extra arguments parsing code

archive: remove extra arguments parsing code

Replace the code that calls backend specific argument parsers by a
simple flag mechanism.  This reduces code size and complexity.

We can add back such a mechanism (based on incremental parse_opt(),
perhaps) when we need it.  The compression level parameter, though,
is going to be shared by future compressing backends like tgz.

Signed-off-by: Rene Scharfe <redacted>
Signed-off-by: Junio C Hamano <redacted>