---
name: Git Commit Helper
description: Generate descriptive commit messages by analyzing git diffs. Use when the user asks for help writing commit messages or reviewing staged changes.
---

# Git Commit Helper

## Quick start

Analyze staged changes and generate commit message:

```bash
# View staged changes
git diff --staged

# Generate commit message based on changes
# (Claude will analyze the diff and suggest a message)
```

## Commit message format

Follow conventional commits format:

```
<type>(<scope>): <description>

[optional body]

[optional footer]
```

### Types

- **feat**: New feature
- **fix**: Bug fix
- **docs**: Documentation changes
- **style**: Code style changes (formatting, missing semicolons)
- **refactor**: Code refactoring
- **test**: Adding or updating tests
- **chore**: Maintenance tasks

### Examples

**Feature commit:**
```
feat(auth): add JWT authentication

Implement JWT-based authentication system with:
- Login endpoint with token generation
- Token validation middleware
- Refresh token support
```

**Bug fix:**
```
fix(api): handle null values in user profile

Prevent crashes when user profile fields are null.
Add null checks before accessing nested properties.
```

**Refactor:**
```
refactor(database): simplify query builder

Extract common query patterns into reusable functions.
Reduce code duplication in database layer.
```

## Analyzing changes

Review what's being committed:

```bash
# Show files changed
git status

# Show detailed changes
git diff --staged

# Show statistics
git diff --staged --stat

# Show changes for specific file
git diff --staged path/to/file
```

## Commit message guidelines

**DO:**
- Use imperative mood ("add feature" not "added feature")
- Keep first line under 50 characters
- Capitalize first letter
- No period at end of summary
- Explain WHY not just WHAT in body

**DON'T:**
- Use vague messages like "update" or "fix stuff"
- Include technical implementation details in summary
- Write paragraphs in summary line
- Use past tense

## Multi-file commits

When committing multiple related changes:

```
refactor(core): restructure authentication module

- Move auth logic from controllers to service layer
- Extract validation into separate validators
- Update tests to use new structure
- Add integration tests for auth flow

Breaking change: Auth service now requires config object
```

## Scope examples

**Frontend:**
- `feat(ui): add loading spinner to dashboard`
- `fix(form): validate email format`

**Backend:**
- `feat(api): add user profile endpoint`
- `fix(db): resolve connection pool leak`

**Infrastructure:**
- `chore(ci): update Node version to 20`
- `feat(docker): add multi-stage build`

## Breaking changes

Indicate breaking changes clearly:

```
feat(api)!: restructure API response format

BREAKING CHANGE: All API responses now follow JSON:API spec

Previous format:
{ "data": {...}, "status": "ok" }

New format:
{ "data": {...}, "meta": {...} }

Migration guide: Update client code to handle new response structure
```

## Template workflow

1. **Review changes**: `git diff --staged`
2. **Identify type**: Is it feat, fix, refactor, etc.?
3. **Determine scope**: What part of the codebase?
4. **Write summary**: Brief, imperative description
5. **Add body**: Explain why and what impact
6. **Note breaking changes**: If applicable

## Interactive commit helper

Use `git add -p` for selective staging:

```bash
# Stage changes interactively
git add -p

# Review what's staged
git diff --staged

# Commit with message
git commit -m "type(scope): description"
```

## Amending commits

Fix the last commit message:

```bash
# Amend commit message only
git commit --amend

# Amend and add more changes
git add forgotten-file.js
git commit --amend --no-edit
```

## Best practices

1. **Atomic commits** - One logical change per commit
2. **Test before commit** - Ensure code works
3. **Reference issues** - Include issue numbers if applicable
4. **Keep it focused** - Don't mix unrelated changes
5. **Write for humans** - Future you will read this

## Commit message checklist

- [ ] Type is appropriate (feat/fix/docs/etc.)
- [ ] Scope is specific and clear
- [ ] Summary is under 50 characters
- [ ] Summary uses imperative mood
- [ ] Body explains WHY not just WHAT
- [ ] Breaking changes are clearly marked
- [ ] Related issue numbers are included
