[Libguestfs] rsync support

Hi Rich et al., Has an rsync addition to libguestfs been considered? It would be great to have when copying the contents of a filesystem to a disk of a different filesystem. It could also be used to keep portions of cloned machines in sync. For example, I'm porting VirtualBox images to Xen. I sometimes make change to the source image that I would like to easily propagate to the Xen copy. DD is sometimes a bit too low-level. Regards, Chris