# Commit Message Generator

## Description
Analyze staged changes and generate conventional commit messages. Supports Conventional Commits, GitHub-style, and custom formats. Can also review existing commit history for consistency.

## Triggers
- "Generate commit message", "Write commit message", "Commit this"
- "What should I commit?", "Review my changes"
- "Commit message for this PR", "Squash and rewrite commits"

## Instructions

### Step 1: Analyze Changes
1. Run `git diff --cached` to see staged changes
2. If nothing staged, run `git diff` and `git status` to show unstaged changes
3. For PR reviews, use `git log --oneline origin/main..HEAD` to see all commits

### Step 2: Categorize Changes
Map changes to conventional commit types:
- `feat`: New feature, new API endpoint, new component
- `fix`: Bug fix, error handling, edge case
- `refactor`: Code restructure without behavior change
- `perf`: Performance improvement
- `docs`: Documentation only
- `style`: Formatting, whitespace, semicolons
- `test`: Adding/updating tests
- `chore`: Build, CI, dependencies, tooling
- `ci`: CI/CD configuration changes
- `revert`: Reverting a previous commit

### Step 3: Generate Message
Format (Conventional Commits):
```
<type>(<scope>): <subject>

<body>

<footer>
```

Rules:
- Subject: imperative mood, lowercase, no period, max 72 chars
- Body: explain what and why, not how, wrap at 72 chars
- Footer: breaking changes (`BREAKING CHANGE:`), issue refs (`Closes #123`)
- If multiple unrelated changes, suggest splitting into separate commits

### Step 4: Multi-commit Suggestion
If staged changes span multiple concerns:
```
Suggested split:
1. feat(auth): add OAuth2 login flow
2. fix(api): handle null response in user endpoint
3. chore(deps): update axios to 1.7.0

Run these commands:
  git reset HEAD
  git add src/auth/oauth.py
  git commit -m "feat(auth): add OAuth2 login flow"
  git add src/api/users.py
  git commit -m "fix(api): handle null response in user endpoint"
  git add package.json package-lock.json
  git commit -m "chore(deps): update axios to 1.7.0"
```

### PR Description Mode
When asked to write a PR description:
1. Read all commits in the branch
2. Categorize by type
3. Generate:
   - Summary (2-3 sentences)
   - Changes (grouped by category)
   - Testing notes
   - Breaking changes (if any)
   - Checklist

## Output Format
Provide 3 options: concise (subject only), standard (subject + body), detailed (subject + body + footer).
Default to standard unless user specifies otherwise.

## Constraints
- Never auto-commit without user confirmation
- For sensitive changes (secrets, auth), add a warning in the footer
- If changes are too large (>20 files), suggest a descriptive PR instead