[libvirt] 'build' on FS pool now unconditionally formats?

Hi guys, Looking at the new FS pool build options and talking with Dave, I see that calling PoolBuild on an FS pool now unconditionally calls mkfs. This is really bad when mixed with virt-manager: previously, we assumed the FS build command was always non destructive (at most it created a directory), so we called it every time, and didn't even allow users to opt out, since there wasn't a use case that called for it. This new formatting behavior really needs to be opt in, otherwise all virt-manager versions creating an FS pool can destroy data. Just FYI, for disk pools (and certain LVM configurations) where this operation has always been destructive, we default to build=off, and loudly warn the user if they choose otherwise. We can do that with this new option as well, but the previous behavior really needs to be reinstated IMO (and before the new release). I fully accept that this could be a bug in virt-manager's assumptions of the build command, but even consider a virsh user: previously build just created a directory, now it formats a partition, without any XML change. Thanks, Cole