AT Protocol repos drop history for a logical clock (repo v3)

What changed

The AT Protocol team announced on August 24, 2023 that repositories no longer keep history in their canonical structure. The repo version becomes 3, prev becomes optional, and a required rev field (a monotonically increasing TID) is added to each signed commit. Rollout began August 28, 2023.

What it means

Code that relies on commit history or the prev field breaks, and ordering must use the new rev field.

Who is affected

Developers who do commit-aware repo sync, check the repo version explicitly, or strictly type-check commits. Most feed generator developers were not affected.

What to do by 28 Aug 2023

Accept repo version 3, stop treating prev as canonical history, and use rev for ordering and for requesting changes since a known revision.