[Libguestfs] missing btrfs subvol support

[Olaf Hering]

On Thu, Oct 16, Olaf Hering wrote:

> I can probably add a check somewhere to catch the whatever=="@". A
> better fix would be to check if a given subvolume is for the entire
> partition.

So after talking to David Sterba there is no way to tell if a given
subvolume is for the entire partition.
Also my attempt to "fix" it by using the -o option is unreliable.

Richard, so what should be done with the root-partition-listed-twice
issue mentioned in the URL above? Just check for a plain '@', assume
thats the entire thing, and skip it to not set is_root=1?

The other bug is that mounting subvolumes in such setup fails anyway
because the subvol= argument lacks the absolute path. It was suggested
to use the "subvolume list" option -a and tweak the resulting list.
There is a <FS_TREE> prefix, which shouldnt be there according to David.

Olaf