Add the OPT_NONEG flag to the "contains" option and its hidden synonym
"with". Since this was added in commit 694a5775 ("git-branch
--contains=commit", 2007-11-07) giving --no-{contains,with} hasn't
been an error, but has emitted the help output since
filter.with_commit wouldn't get set.

Now git will emit "error: unknown option `no-{contains,with}'" at the
top of the help output.
Signed-off-by: NÆvar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>