* WIP. Typos and logging.
* Format todos
* Pause pruning while a snapshot is under way
Logs, docs and todos
* Allocate memory for the full chunk
* Name snapshotting threads
* Ensure `taking_snapshot` is set to false whenever and however `take_snapshot`returns
Rename `take_at` to `request_snapshot_at`
Cleanup
* Let "in_progress" deletion fail
Fix tests
* Just use an atomic
* Review grumbles
* Finish the sentence
* Resolve a few todos and clarify comments.
* Calculate progress rate since last update
* Lockfile
* Fix tests
* typo
* Reinstate default snapshotting frequency
Cut down on the logging noise
* address grumble
* Log memory use with `journal_size()` and explain why.
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