+dit(bf(--protocol=NUM)) Force an older protocol version to be used. This
+is useful for creating a batch file that is compatible with an older
+version of rsync. For instance, if rsync 2.6.4 is being used with the
+bf(--write-batch) option, but rsync 2.6.3 is what will be used to run the
+bf(--read-batch) option, you should use "--protocol=28" (when creating the
+batch file) to force the older protocol version to be used in the batch
+file (assuming you can't upgrade the rsync on the reading system to 2.6.4).
+