libvirt users - Sep 2019 - Disk backup for live and offline domains

Hi,

I followed the instructions on the wiki
https://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit
for a live disk backup. Unfortunately this is not working when the
domain is offline because the active blockcommit throws

error: Requested operation is not valid: domain is not running

For my use case it should be possible for the domain to shut down while
the backup is in progress. I'm looking for a way to shorten the backing
chain after the backup finishes and the domain is offline.

Is there a way to let libvirt decide wether to shorten the backing chain
using blockcommit or some alternative way which works on offline
domains?

As I'm writing this I might as well ask about the current state of
"incremental backups". It seems like dirty bitmaps can keep track of
which blocks changed and just copy those to the backup. Is there some
libvirt command-line frontend for that or is it planned for the future?

Thanks.

- Tim