log: fix --quiet synonym for -s

log: fix --quiet synonym for -s

Originally the "--quiet" option was parsed by the
diff-option parser into the internal QUICK option. This had
the effect of silencing diff output from the log (which was
not intended, but happened to work and people started to
use it). But it also had other odd side effects at the diff
level (for example, it would suppress the second commit in
"git show A B").

To fix this, commit 1c40c36 converted log to parse-options
and handled the "quiet" option separately, not passing it
on to the diff code. However, it simply ignored the option,
which was a regression for people using it as a synonym for
"-s". Commit 01771a8 then fixed that by interpreting the
option to add DIFF_FORMAT_NO_OUTPUT to the list of output
formats.

However, that commit did not fix it in all cases. It sets
the flag after setup_revisions is called. Naively, this
makes sense because you would expect the setup_revisions
parser to overwrite our output format flag if "-p" or
another output format flag is seen.

However, that is not how the NO_OUTPUT flag works. We
actually store it in the bit-field as just another format.
At the end of setup_revisions, we call diff_setup_done,
which post-processes the bitfield and clears any other
formats if we have set NO_OUTPUT. By setting the flag after
setup_revisions is done, diff_setup_done does not have a
chance to make this tweak, and we end up with other format
options still set.

As a result, the flag would have no effect in "git log -p
--quiet" or "git show --quiet".  Fix it by setting the
format flag before the call to setup_revisions.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>