Detect "snapper-style" subvolume tree, and populate Delta-Incremental-style backup.
butterback detects parent-child subvolume relations, and sets the parent as
-p. Scanning a tree of
snapper snapshots currently yields in either all of them going full-backup (which means every new snapper-snapshot will be uploaded in full!), or all delta'd against the main volume when it's included (which means data gets uploaded twice).
/ /.snapshots /.snapshots/1 /.snapshots/2
Then, ideally, we have them like this initially:
/.snapshots (Full) /.snapshots/1 (Full) /.snapshots/2 (Delta on /.snapshots/1) / (Delta on /.snapshots/2)
and after initial backup
/.snapshots (Incremental on /.snapshots) /.snapshots/1 (No change) /.snapshots/2 (No change) /.snapshots/3 (Incremental on /.snapshots/2) / (Delta on /.snapshots/2)
/ should be possible to be left out.