Feature suggestion: --write-batch --dry-run

[Peter Hartley]

AFAICS, --write-batch logs the changes made while doing an rsync
operation from place A to place B, and lets you then use the batch file
to apply those changes to place C if it were hitherto the same as B. I
reckon it'd be a good feature to have a mode where the changes can be
logged *without* updating B, so that the update to B itself can be done
from the batch file.

The motivation for this is wanting to synchronise a large directory tree
between Site A and Site B. They can only communicate directly through a
slow network link, but I often *visit* Site B from Site A while carrying
several Gbytes' worth of Ipod.

So it would be cool if Site A could use the network connection to work
out what needed doing, but not actually send any new files over --
instead just writing a batch file which I could then carry over to B and
apply. (I can't just rsync Site A onto my Ipod, and then rsync it again
at the other end, because the Ipod is much smaller than the total size
of the directory tree, even though it's much larger than any one update
would be. Nor do I really want to have *two* copies of the directory
tree at Site A in order to use traditional --write-batch.)

Even better, of course, would be to find out that this sort of operation
was *already* possible using some rsync features I missed when looking
into this...

	Peter