Currently the incremental backup bitmap is strictly additive. Any changes from the start of this ID to a table are noted in the set bits. Once a bit is set, it is never unset for that backup ID. But a file can undergo a lot of checkpoints between incremental backups and some blocks that were changed earlier may not be relevant to any currently valid checkpoints. That means we're copying data unnecessarily.

Explore what it would take to recreate a full/correct bitmap after a checkpoint completes based on what blocks are valid currently.