275267937b (range-diff: make dual-color the default mode, 2018-08-13)
replaced --dual-color with --no-dual-color but left the option's
summary untouched. Rewrite the summary to describe --no-dual-color
rather than dual-color.
Helped-by: Jonathan Nieder <jrnieder@gmail.com> Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Kyle Meyer <kyle@kyleam.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>