RFE: 'btrfs' tools machine readable output

["Richard W.M. Jones" <rjones@redhat.com>]

I don't have time to implement this right now, so I'm just posting
this as a suggestion/request ...

It would be really helpful if the btrfs tools had a machine-readable
output.

Libguestfs parses btrfs tools output in a number of places, eg:
https://github.com/libguestfs/libguestfs/blob/master/daemon/btrfs.c
This is a massive PITA because each time a new release of btrfs-progs
comes along it changes the output slightly, and we end up having
to add all sorts of hacks.

With machine-readable output, there'd be a flag which would
change the output.  eg:

$ btrfs filesystem show
Label: 'ROOT'  uuid: af471cfc-421a-4d51-8811-ce969f76828a
        Total devices 1 FS bytes used 5.29MiB
        devid    1 size 767.97MiB used 92.00MiB path /dev/sda2

would become:

$ btrfs --json filesystem show
{
  "devices": {
     "Label": "ROOT",
     "uuid": "af471cfc-421a-4d51-8811-ce969f76828a",
     /// etc
  }
}

By this example I don't mean that JSON has to be the format -- in fact
it's a terrible format with all sorts of problems -- any format which
is parseable with C libraries would do for us.

Rich.

-- 
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