[PATCH] Finish initial cut of git-pack-object/git-unpack-object pair.

[PATCH] Finish initial cut of git-pack-object/git-unpack-object pair.

This finishes the initial round of git-pack-object /
git-unpack-object pair.  They are now good enough to be used as
a transport medium:

 - Fix delta direction in pack-objects; the original was
   computing delta to create the base object from the object to
   be squashed, which was quite unfriendly for unpacker ;-).

 - Add a script to test the very basics.

 - Implement unpacker for both regular and deltified objects.

Signed-off-by: Junio C Hamano <redacted>
Signed-off-by: Linus Torvalds <redacted>