[Qemu-devel] [RFC] Allow 'qemu-img convert' to preserve the backing file

[Marc Bevand]

Currently if qemu-img convert is used to convert for example a qcow1 image (with
a backing file) to a qcow2 image, the resulting image will have no backing file.

In order to preserve the backing file (to save disk space), qemu-img should
offer a command line option to enable the feature. For this it needs to be made
aware of BlockDrivers supporting backing files.

I need this feature and am going to implement it. If someone has any comment to
make, now is the time.

-marc