Document git-diff whitespace flags -b and -w
Document git-diff whitespace flags -b and -w

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 <a6a1517a087f9f64a72f41a0de57ff01fbb0e412@gmail.com>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git