Did some prototyping. Did a snapshot of an existing cluster. Then added a new index and a few documents to it, and did another snapshot. Then did some messing with that new index (deleted, changed, and added docs) and did a third snapshot.
Then did a restore to the first snapshot, then the second, and then the third, checking what was there for each step.
This would be good to perhaps make explicit in the snapshot/restore documentation, that you can do repeated snapshots / restores for a migration. i.e. to the 'big' one in advance and restore it into the new cluster, then a final delta at the time of the migration and restore that final snapshot into the new cluster.
Thanks!
Bob.