0.9.0

A review of 0.8.0 — the release written to fix the previous review — found three more defects. A fix release nobody reviewed is the same shape as the thing it was fixing, so it was reviewed.

Fixed

• With the remote as authority, a refused local write was swallowed. 0.8.0 fixed exactly this for Authority::Local and left the mirror case: the authority takes the write, the local copy refuses it — a full disk is enough — and the caller got an error while divergences() stayed empty and catch_up() was a no-op. Every later write then computed its expectation from the stale local revision and was refused by the authority for ever, with no record of why. It is recorded as a divergence now, saying which way round it happened.

• catch_up could never clear a divergence against a replica at revision 0. None and Some(0) were collapsed, so a replica genuinely holding a revision-0 instance was given Expect::Absent, which cannot match. Unreachable through entity-core, which creates at revision 1 — and reachable for any third-party Store used as the replica, which is exactly who this protocol is for.

• Three refusal messages had lost their line continuations and carried 26 to 38 consecutive spaces into what a person reads.

Changed

• The wire version is entity.store/2. Answer is a tagged enum with deny_unknown_fields, so adding a variant is a breaking wire change: a peer built against /1 cannot decode {"answer":"refused"}. 0.8.0 added Refused and Unreachable and left the version at /1, which made the refusal undecodable by exactly the peer it exists to inform — it would have arrived as a decode failure, which is the Backend outcome that change set out to avoid.

  A /1 peer is now refused by name, which is what a version is for.