Module diff 

Engine::diff(ref_a, ref_b) implementation for git-branch mounts.

Walks the two tree objects pointed to by ref_a and ref_b inside the workspace’s mem-repo gitdir, produces a per-entity diff (Diff) that downstream replay / review / preview / audit tooling consumes. Same backbone the changes_since op uses — two-tree diff with rename detection — but expanded into a two-endpoint shape with optional content enrichment.

V1 scope

• Added / Modified / Deleted entries from a vanilla gix tree-diff.
• Content enrichment per DiffConfig::include_content.
• InvalidEntity entries for paths that fail UTF-8 / parse.

V1 gaps (handover candidates)

• Rename detection: deferred. The agent-notes-driven rename collapse changes_since performs requires a since cursor in the same mem’s history. A generic two-ref diff (potentially cross-mem) needs a different walk; v1 emits Added/Deleted pairs instead of Renamed and leaves rename-chain unfilled.
• Cross-entity ripple: IncomingRipple lists stay empty in the entries. Populating them requires a per-side wiki-link graph reconstruction that the engine’s current in-memory store does not maintain for arbitrary refs.

Functions

diff_two_refs

Two-ref structural diff. See module docs for the v1 scope and the known gaps (rename, ripple) that will surface as handover items.