only keep last required snapshot when backup disk is disconnected?

[karme]

I am not quite sure if my understanding is correct but I think if the backup target isn't available no cleanup is done at all?

I get something like:

WARNING: Skipping cleanup of snapshots for subvolume "/mnt/btr_pool/@rootfs", as at least one target aborted earlier
WARNING: Skipping cleanup of snapshots for subvolume "/mnt/btr_pool/@homefs", as at least one target aborted earlier

in this case.

Maybe this could be improved to remove all old snapshots not required to do an incremental backup?