Using rsync to generate diff/patches

[Dave Whitinger]

I've been using rsync to remotely backup my MySQL databases
(totalling over 3 gigabytes) and it works nice and fast.

Now I'm trying to setup my system to save yesterday's backup
before applying today's backup, but it's not really feasible to
keep a 3gig backup for each day, and I'd rather just store diffs
from the previous day.  This way, I can just go back in time by
applying the diffs.

I'm wondering if rsync can be used for this; here's how I
envision it working:

1) The rsync process works just like normal, except instead of
applying the changes to the destination files, it instead
generates one big file that contains all the TODO changes.

2) The administrator later can run rsync with a certain switch,
and feed it this generated file through stdin, and those changes
are applied.

Great idea, no?

Dave