Document git diff options -b / --ignore-space-change and
-w / --ignore-all-space, introduced by Johannes Schindelin
in commit 0d21efa5, "Teach diff about -b and -w flags".
The description of options is taken from GNU diff man page and
GNU Diffutils info documentation.
Signed-off-by: Jakub Narebski <jnareb@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>