Timeline

Fills in the TODO stub in repo_history.go so Repo.Diff returns a real unified diff for a file between two checkins instead of a "not yet implemented" error.

The implementation piggybacks on internal/diff.Unified, which already produces Myers-algorithm output. A small blobAt helper walks the manifest at each checkin, resolves the file's UUID to a blob RID, and expands the content. An absent file on a side is treated as empty bytes so pure additions and deletions render as clean insert/delete hunks. Identical content on both sides returns an empty slice rather than a DiffEntry with an empty Unified string, which keeps callers from having to distinguish "no diff" from "missing output".

Adds repo_history_test.go covering modification, identical content, addition, deletion, absent-both-sides, and the empty-filePath error. check-in: a3fbae135e user: [email protected] tags: trunk