Fix archive format with -- on the command line

Fix archive format with -- on the command line

Giving --format from the command line, or using output file extention to
DWIM the output format, with a pathspec that is disambiguated with an
explicit double-dash on the command line, e.g.

    git archive -o file --format=zip HEAD -- path
    git archive -o file.zip HEAD -- path

didn't work correctly.

This was because the code reordered (when one was given) or added (when
the format was inferred) a --format argument at the end, effectively
making it to "archive HEAD -- path --format=zip", i.e. an extra pathspec
that is unlikely to match anything.

The command line argument list should always be "options, revs and then
paths", and we should set a good example by inserting the --format at the
beginning instead.

Reported-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>