blame: fix coloring for repeated suspects

blame: fix coloring for repeated suspects

The option --ignore-rev passes the blame to an older commit.  This can
cause adjacent scoreboard entries to blame the same commit.  Currently
we only look at the present entry when determining whether a line needs
to be colored for --color-lines.  Check the previous entry as well.

Reported-by: Seth McDonald <sethmcmail@pm.me>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>