I added this option in git-checkout and git-merge in c1d7036b6b
(checkout,merge: disallow overwriting ignored files with
--no-overwrite-ignore - 2011-11-27) but did not remember to update
documentation. This completes that commit.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>