Allow dedup of RO snapshots

[HaleTom]

Currently, bedup doesn't support deduping in RO snapshots:

This approach doesn't require special kernel support, but it has two downsides: locking has to be done in userspace, and there is no way to free space within read-only (frozen) snapshots.

duperemove allows dedup of RO snapshots with its -A option

Could beup support this, too?

[MarcelWaldvogel]

A (not really elegant) workaround would be to

btrfs property set "$dir" ro false
bedup dedup "$dir"
btrfs property set "$dir" ro true

It worked for me with a simple loop over all my snapshots. If your readonly snapshots are not all in the same directory, you might want to wrapped it in a loop over btrfs subvolume list … and testing for btrfs propert get … ro