Import bup git package as wip/bup-git.

bup is a program that backs things up.  bup has a few advantages
over other backup software:

It uses a rolling checksum algorithm (similar to rsync) to split
large files into chunks. The most useful result of this is you can
backup huge virtual machine (VM) disk images, databases, and XML
files incrementally, even though they're typically all in one huge
file, and not use tons of disk space for multiple versions.

It uses the packfile format from git (the open source version
control system), so you can access the stored data even if you
don't like bup's user interface.

Unlike git, it writes packfiles directly (instead of having a
separate garbage collection/repacking stage) so it's fast even with
gratuitously huge amounts of data. bup's improved index formats
also allow you to track far more filenames than git (millions) and
keep track of far more objects (hundreds or thousands of gigabytes).

Data is "automagically" shared between incremental backups without
having to know which backup is based on which other one - even if
the backups are made from two different computers that don't even
know about each other. You just tell bup to back stuff up, and it
saves only the minimum amount of data needed.
+ bup-git.