+ - You may specify --max-delete=0 to a 3.0.0 client as long as the
+ receiving side is at least version 3.0.0. This means that you
+ can pull from an older rsync with this option, but pushing to an
+ older rsync will generate an error. *Be careful to never specify
+ a 0 value to older rsync client, or it will be silently ignored.*