Offline sync rool a la rsync ?

[Gregor Hoffleit <gregor@mediasupervision.de>]

I'm looking for a tool like rsync that's able to work in offline mode.
Imagine a machine has no internet connection, but keeps a repository of
files. At another machine, there's a second instance of that repository. Now
I'd like to be able to use e.g. a zip disk to carry the changes from one
site to the other and back.

In the simplest case, I could keep a filelist of both repositories on the
zip disk, and every time a file is in the local repository, but not in the
other, it would be copied to the disk. More elaborate versions of the
algorithm could involve checksums and/or date checks.

Does something like this already exist ?

    Gregor