If the user specifiers "normal" for a foreground color, this
should be a noop (while this may sound useless, it is the
only way to specify an unchanged foreground color followed
by a specific background color).
We also check that color "-1" does the same thing. This is
not documented, but has worked forever, so let's make sure
we keep supporting it.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>