[PATCH] Add git-apply-patch-script.

I said:

- Stop attempting to be compatible with cg-patch, and drop
(mode:XXXXXX) bits from the diff.

- Do keep the /dev/null change for created and deleted case.

- No "Index:" line, no "Mode change:" line, anywhere in the
output.  Anything that wants the mode bits and sha1 hash can
do things from GIT_EXTERNAL_DIFF mechanism.  Maybe document
suggested usage better.

This adds an example script git-apply-patch-script, that can be
used as the GIT_EXTERNAL_DIFF to apply changes between two trees
directly on the current work tree, like this:

GIT_EXTERNAL_DIFF=git-apply-patch-script git-diff-tree -p <tree> <tree>

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>