If we have a "--" flag, we should not be doing DWIM magic
based on whether arguments can be filenames. Reorder the
conditional to avoid the check_filename() call entirely in
this case. The outcome is the same, but the short-circuit
makes the dependency more clear.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>