On OSX 10.8.5, rsync 3.1.0 introduces a new bug. Doing:
rsync -ntrlvhb --delete --backup-dir=foo source dest
when the dir "foo" already exists will cause rsync to display:
"sending incremental file list
Created backup_dir foo/"
I can understand displaying this message if foo really did need to be created, but it's already there and waiting, and has been used as backup-dir before. 3.0.9 and earlier don't do this.
Also, when the same command is run without the '-n' flag, rsync acts correctly and won't display the "Created backup_dir foo/" message.
I'm checking in a fix for this now. Thanks!