[Libguestfs] [PATCH v2v 0/3] Implement -of qcow2 -oo compressed

Pre-modularised virt-v2v allows you to use either --compress or -oo compressed which basically added the -c option to qemu-img convert, compressing the qcow2 output. Since we switched over to nbdcopy this option is no longer available. The alternative is to set up the "compress" driver in qemu-nbd. However that didn't work because nbdcopy used to ignore the target minimum block size, and the compress driver requires you to obey the 64k minimum when writing, else it fails. Now that nbdcopy 1.13.5 actually fixes this problem, we can reimplement -oo compressed. This is a minimal fix for https://bugzilla.redhat.com/show_bug.cgi?id=2047660 I only implemented this for small selection of output modes that go to local files. Old virt-v2v also implemented this option (at least, in theory) for -o glance, -o rhv and -o vdsm, but all of these modes are deprecated to some degree. -o openstack which replaces glance only allows raw format uploads, and -o rhv-upload which replaces -o rhv/vdsm does its own thing completely. Rich.