Mac – rsync chokes on read-only files

I'm using rsync on Mac to back up to a USB drive or a network image (also HFS+ formatted). I'm having trouble with files from .svn subdirectories, such as 'all-wcprops' or 'entries' — when checking out or updating, Subversion marks them as read-only (permissions bits are 444).

My rsync command chokes on that; they are backed up correctly during the first run, but any changes cause "permission denied" errors on target (backup volumes).

Maybe it's an artefact of Tortoise SVN – I'm actually using it from an XP virtual machine to do svn operations. But not using Tortoise is not an option.

How can I fix it? I spent some time trawling through rsync manuals and all the proper flags seem to be set. Can't find anything in Tortoise prefs either to allow me to tell it not to mark these files read only.

Here is my rsync command:

rsync -aNHAX --inplace --verbose --delete --delete-excluded --fileflags --force-change --exclude-from=.rsync/exclude-list ~ $backup_dir