Comment 2 for bug 326369

You shouldn't run 'pack' at all. Generally, bzr takes care of tuning
your repository. You definitely should not run it before rsyncing,
because you don't want to rsync data you have before - and packing all
the data into one file will case rsync to copy it from scratch.

You're right that the docs here could and should be expanded.

As for the reason, we keep a backup of files removed by a write
operation, removed the next time such a backup is needed. We do this
because various network servers are not as reliable as we might like,
and in the event of a failure where new data hasn't hit disk but a
delete or move has, its much safer to have issued a move (which can be
reverted) than a delete (which requires an undelete capability on that
filesystem).

-Rob