0.21.0

Added

• entity-eventlog feature tree: EventlogRecordedStoreOwner::Tree and EventlogRecordedStoreProvisioner::Tree open and prepare a recorded store on eventlog-tree, whose immutable files merge under version control. Two branches that recorded decisions for different subjects merge into one store that opens and holds both.
• Forked subjects:
  • StoredRecord.lineage carries each record's digest and parents when the provider keeps them.
  • A history with lineage is verified branch by branch: each record is checked against its parent's state.
  • A subject both branches changed is reported as AsyncStoreError::Forked with its heads, instead of CorruptHistory for the whole store. Other subjects keep serving; reads and ordinary writes of the forked subject refuse.
  • branch_heads lists a history's heads and their states.
• BatchAction::Merge joins a forked subject. It executes one operation on the state the chosen head reached, at the highest revision any head reached. The append joins every head, and the subject serves again at the next revision.
• Refused commands are recorded:
  • Executor::recording_refusals records each kernel refusal, expectation conflict and write to a forked subject as a RecordedRefusal, before returning the refusal.
  • EventlogOperationStore implements AsyncRefusalRecorder: one er.refused_request event per distinct refusal on its own er.refusal stream, with the content in a blob. A retry refused for the same reason is the same record, and no subject's revision moves.

Changed

• Eventlog is pinned at the 0.4.0 release (70096af8), which adds eventlog-tree and the fork vocabulary this release uses.
• The tree owner opens eventlog-tree with the recorded projector registered before the replay, so an open replays the history once instead of twice.
• AppendMember gains merge, and StoredRecord gains lineage. Code that builds either with a struct literal adds the field; AppendMember::new sets merge: None.