Re: [libvirt] [RFC] Introduce virDomainBlockCopy API

This API starts asynchronous live copy of a block device (specified by target element of the xml argument) into a new source (which must already exist). The process can be controlled in the same way as migration: monitored with virDomainJobInfo() and canceled using virDomainAbortJob(). I don't particularly like the name (but I wasn't able to come up with a better one) since it doesn't reflect the fact that once a block device is switched to use the new source once copying finishes. In other words, the goal of this API is to update the device to use new source (just like virDomainUpdateDeviceFlags) but before doing so all data is copied from the old source into the new one (unlike the UpdateDevice API).