Diff Scope

Step 2: Get the Current Diff

1. Get the merge base:

   git merge-base origin/master HEAD
   

2. Get all committed changes in this branch:

   git diff $(git merge-base origin/master HEAD)...HEAD --stat
   git diff $(git merge-base origin/master HEAD)...HEAD --name-only
   

3. Get uncommitted changes:

   git diff --stat
   git diff --cached --stat
   

4. Read the actual diffs for context:

   git diff $(git merge-base origin/master HEAD)...HEAD
   

Step 3: Map Changes to Acceptance Criteria

For each acceptance criterion from the ticket:

1. Determine status: Does the current diff address this criterion?

   • DONE — changes clearly implement this criterion
   • PARTIAL — some work done, more needed
   • NOT STARTED — no changes related to this criterion
   • UNCLEAR — changes exist but unclear if they satisfy the criterion

2. Cite evidence: Reference specific files and changes that address (or fail to address) each criterion.

Step 4: Detect Scope Drift

Identify changes that do NOT map to any acceptance criterion:

1. List files changed that are not related to any AC item
2. For each unplanned change, classify:
   • NECESSARY — required to implement an AC item (e.g., fixing a broken import)
   • RELATED — reasonable cleanup in the area (e.g., fixing a typo in a file you touched)
   • DRIFT — unrelated work that should be a separate PR

Step 5: Present the Scope Report

## Scope Check — CDIN-{number}

### Acceptance Criteria Status
| # | Criterion | Status | Evidence |
|---|-----------|--------|----------|
| 1 | {AC text} | DONE | `{file}`: {what was done} |
| 2 | {AC text} | PARTIAL | `{file}`: {what's done, what's missing} |
| 3 | {AC text} | NOT STARTED | — |

### Unplanned Changes
| File | Classification | Reason |
|------|---------------|--------|
| `{file}` | NECESSARY | {why} |
| `{file}` | DRIFT | {what it does — suggest splitting} |

### Summary
- **AC coverage:** {X}/{Y} criteria addressed
- **Scope drift:** {None / Minor / Significant}
- **Recommendation:** {Continue / Split unrelated changes / Refocus on missing AC items}

Step 6: Suggest Next Action

Based on the report:

• If all AC items are DONE and no drift: "Looking good. Run /diff:diff-check for a self-review before committing."
• If AC items are PARTIAL/NOT STARTED: "Focus on: {list missing items}"
• If significant drift detected: "Consider splitting these files into a separate PR: {list}"