Re: [libvirt] [PATCHv2 9/9] RFC: conf: introduce <format> as synonym of <driver type=...>

Still an RFC, since this claims over 400 tests are impacted: $ git grep '<driver.*type=\(\(.\)[a-zA-Z0-9]*\2\)' tests/*data/ | wc Most uses of <driver> are per-disk - they affect the way the hypervisor exposes storage to the guest, regardless of how many host resources are involved. But one attribute, the format, is something associated with each host resource, since it is possible to have a chain of files of different formats. What's more, the <volume> XML of storage volume APIs already has a <format type='...'/> element. This patch adds a <format type='...'/> element to each <disk>'s <source> within a <domain>. For back-compat, we still output the format of the top-level resource in the <driver> element; and accept either spelling on input (if both spellings are given, they must match); but once the XML is extended to show full backing chain in <domain>s, the backing files will have only a <format> element, and no extra <driver> elements.