clare: Skill for Codex

Review Diff vs. Base Ref

Scope and Baseline

Review all changes on the current branch against an appropriate base ref — as if performing a thorough pull-request code review. Do not guess at correctness; read the actual diff and the relevant file context.

---

Step 1 — Determine the Base Ref

Resolve the base ref in priority order. Use the first one that succeeds:

1. User-specified — if the user says "review vs main", "against origin/staging", etc., use that ref.
2. Upstream tracking branch — git rev-parse --verify "upstream/$(git symbolic-ref --short HEAD 2>/dev/null)" 2>/dev/null
3. Origin tracking branch (same name) — git rev-parse --verify "origin/$(git symbolic-ref --short HEAD 2>/dev/null)" 2>/dev/null
4. origin/main — git rev-parse --verify origin/main 2>/dev/null
5. origin/master — git rev-parse --verify origin/master 2>/dev/null
6. Local main — git rev-parse --verify main 2>/dev/null
7. Ask — if none resolve, say: "I couldn't determine a base branch. What should I diff against?"

---

Step 2 — Gather the Diff

# Unified diff from merge base (PR semantics — use triple-dot)
git diff <BASE_REF>...HEAD

# File summary (what changed at a glance)
git diff --stat <BASE_REF>...HEAD

# Untracked new files not yet committed
git status --short

Read the complete diff before beginning the review. Do not review hunks in isolation.

---

Step 3 — Load File Context

For every file that appears in the diff, read the full file — not just the changed hunks. This is required to:

• Detect misuse of a new or changed API by its callers
• Verify that error handling is consistent with the rest of the file
• Identify invariants that the changed code may break
• Confirm that imports, exports, and type signatures are consistent

---

Review Checklist

Apply every category below to every changed file. Do not skip a category because the change looks small — subtle bugs hide in small diffs.

---

1. Correctness & Logic