[PATCH] fix scalability problems with git-deltafy-script

[PATCH] fix scalability problems with git-deltafy-script

Current version would spin forever and exhaust memory while attempting
to sort all files from all revisions at once, until it dies before even
doing any real work.  This is especially noticeable when used on a big
repository like the imported bkcvs repo for the Linux kernel.

This patch allows for batching the sort to put a bound on needed
resources and making progress early, as well as including some small
cleanups.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>