Why: depth 1 makes prev_sha and sha unrelated shallow roots, so update reports a fork instead of an upgrade. Evidence: SELF the pin-fetch credential test; CI run 2829 showed the fork message. Impact: test-pg fetches 200 commits from each pin, not the full history. Refs: .task/feature-svc-d3-real-scenarios.md Co-authored-by: Cursor <cursoragent@cursor.com>