[libvirt-users] libvirt support for qcow2 rebase?

I have not found support in libvirt (nor virsh) for doing the equivalent of "qemu-img rebase ....". The use case: You have copied a qcow2 stack and the new files have different names or reside in a different directory. Therefore you need to change the backing file. Is there a way to do this? Is this a planned addition to libvirt? Harald