Using rsync for versioned backups without --backup

[Kelly Jones]

I want to use rsync to backup a large file (say 1G) that changes a
little each day (say 1M), but I also want the ability to re-create
older versions of this file.

I could use --backup, but that would create a 1G file each day, even
though I only "really" need the 1M that's changed.

How do I tell rsync: "while updating, also store the changes you'd
need to convert today's backup into yesterday's backup"?

I realize I could use diff or something, but since rsync has to
calculate minimal changes anyway, it'd be nice to store them.

I thought the --itemize-changes option might do this, but no.

-- 
We're just a Bunch Of Regular Guys, a collective group that's trying
to understand and assimilate technology. We feel that resistance to
new ideas and technology is unwise and ultimately futile.