rev-list: fix showing distance when using --bisect-all

rev-list: fix showing distance when using --bisect-all

Before d467a52 ("Make '--decorate' set an explicit 'show_decorations'
flag", Nov 3 2008), commit decorations were shown whenever they exist, and
distances stored in them by "git rev-list --bisect-all" were automatically
shown.  d467a52 changed the rule so that commit decorations are not shown
unless rev_info explicitly asks to, with its show_decorations bit, but
forgot that the ones "git rev-list --bisect-all" adds need to be shown.

This patch fixes this old breakage.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>