This option was specified to parseopt as an OPT_BIT; however, we
actually want to _set_ the bit on --no-empty-directory. Thus the
existing implementation used --no-empty-directory, and required
--no-no-empty-directory to negate it.
Now that OPT_NEGBIT exists, we can properly support it as
--empty-directory and --no-empty-directory (but of course
still defaulting to showing empty directories).
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>