changelog-writer — Claude Code skill: changelog from git commits

---
name: changelog-writer
description: Generates changelogs and release notes from git commits, PR titles, and issue references. Organizes changes by impact type (breaking, features, fixes, improvements), formats according to Keep a Changelog standard, and provides version tagging and semantic versioning suggestions. Use when users request "create changelog", "write release notes", "document version changes", or "prepare release".
---

# Changelog & Release Notes Writer

Generate professional changelogs and release notes from version control history.

## Core Workflow

1. **Analyze commits**: Parse git history since last release
2. **Categorize changes**: Group by type (feat, fix, docs, etc.)
3. **Identify breaking changes**: Flag incompatible changes
4. **Extract highlights**: Surface most important changes
5. **Format document**: Follow Keep a Changelog format
6. **Suggest version**: Recommend semantic version bump
7. **Generate release notes**: Create user-friendly summary

## Commit Analysis

### Extract Information From

- Commit messages (preferably conventional commits)
- PR titles and descriptions
- Issue references (#123)
- Merge commit messages
- Commit authors

### Parse Patterns

```
feat(auth): add OAuth2 support
^    ^      ^
|    |      └─ Description
|    └─ Scope (optional)
└─ Type
```

**Types to Categories:**

- `feat` → Added
- `fix` → Fixed
- `docs` → Documentation
- `style`, `refactor` → Changed
- `perf` → Performance
- `test` → Testing
- `chore`, `ci` → Internal
- `BREAKING CHANGE` → Breaking Changes

## Changelog Format (Keep a Changelog)

```markdown
# Changelog

All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [Unreleased]

### Added

- New feature X
- Support for Y

### Changed

- Updated Z behavior

### Fixed

- Resolved issue #123

## [2.1.0] - 2024-01-15

### Added

- OAuth2 authentication support
- User profile management API
- Dark mode toggle

### Changed

- Improved error messages
- Updated dependencies to latest versions

### Deprecated

- Legacy authentication method (will be removed in 3.0.0)

### Fixed

- Memory leak in WebSocket connection
- Incorrect date formatting in reports
- Race condition in concurrent requests

### Security

- Patched XSS vulnerability in user input

## [2.0.0] - 2023-12-01

### Breaking Changes

- ⚠️ Removed support for Node.js 16
- ⚠️ Changed API response format for `/users` endpoint
- ⚠️ Renamed `config.yaml` to `config.yml`

### Added

- Complete API rewrite with improved performance
- WebSocket support for real-time updates

### Migration Guide

See [MIGRATION_v2.md](./docs/MIGRATION_v2.md) for upgrade instructions.

[unreleased]: https://github.com/user/project/compare/v2.1.0...HEAD
[2.1.0]: https://github.com/user/project/compare/v2.0.0...v2.1.0
[2.0.0]: https://github.com/user/project/releases/tag/v2.0.0
```

## Release Notes Format

````markdown
# Release v2.1.0 - "Feature Release Name"

Released: January 15, 2024

## 🎉 Highlights

This release brings major improvements to authentication and user experience:

- **OAuth2 Support**: Users can now sign in with Google, GitHub, and Microsoft
- **Dark Mode**: Toggle between light and dark themes
- **Performance**: 40% faster API response times

## ✨ New Features

- OAuth2 authentication with popular providers (#456)
- User profile management API (#478)
- Dark mode toggle in settings (#492)
- Export data in CSV format (#501)

## 🐛 Bug Fixes

- Fixed memory leak in WebSocket connections (#489)
- Resolved incorrect date formatting in reports (#495)
- Fixed race condition in concurrent API requests (#503)

## 🔄 Changes

- Improved error messages across the application
- Updated all dependencies to latest stable versions
- Refined UI animations for smoother experience

## 🔒 Security

- Patched XSS vulnerability in user input validation
- Updated JWT library to address CVE-2024-1234

## 📚 Documentation

- Added OAuth2 setup guide
- Updated API reference with new endpoints
- Improved troubleshooting section

## 🙏 Contributors

Thank you to all contributors who made this release possible:

- @alice - OAuth2 implementation
- @bob - Dark mode feature
- @charlie - Bug fixes and testing

## 📦 Installation

```bash
npm install [email protected]
# or
yarn add [email protected]
```
````

## 🔗 Links

- [Full Changelog](https://github.com/user/project/compare/v2.0.0...v2.1.0)
- [Documentation](https://docs.projectname.com)
- [Migration Guide](./docs/MIGRATION_v2.md)

---

**Note:** This is a minor release. No breaking changes. Safe to upgrade from 2.0.x.

````

## Semantic Versioning Rules

Given a version number MAJOR.MINOR.PATCH (e.g., 2.1.0):

1. **MAJOR** (2.x.x → 3.x.x)
   - Breaking changes
   - Incompatible API changes
   - Removed features

2. **MINOR** (2.1.x → 2.2.x)
   - New features
   - Backward-compatible functionality
   - Deprecated features

3. **PATCH** (2.1.0 → 2.1.1)
   - Bug fixes
   - Security patches
   - Performance improvements

**Special versions:**
- `0.x.x` - Initial development (breaking changes allowed in minor)
- `x.y.0-alpha.1` - Pre-release
- `x.y.0-beta.2` - Beta release
- `x.y.0-rc.1` - Release candidate

## Git Commands for Changelog Generation

```bash
# Get commits since last tag
git log $(git describe --tags --abbrev=0)..HEAD --oneline

# Get commits between two tags
git log v2.0.0..v2.1.0 --oneline

# Get commits with PR numbers
git log --merges --pretty=format:"%s" v2.0.0..HEAD

# Get contributors
git log v2.0.0..HEAD --format='%aN' | sort -u

# Get commit count by type
git log v2.0.0..HEAD --oneline | grep -E '^[a-f0-9]+ (feat|fix|docs)' | cut -d' ' -f2 | sort | uniq -c
````

## Breaking Changes Detection

Look for these indicators:

- Commit message contains `BREAKING CHANGE:`
- Commit type has `!` (e.g., `feat!:`)
- PR labeled with "breaking-change"
- Major dependency updates
- API endpoint changes
- Config file format changes

**Document clearly:**

````markdown
### Breaking Changes

⚠️ **API Response Format Changed**

The `/api/users` endpoint now returns:

```json
// Before
{ "data": [...] }

// After
{ "users": [...], "total": 100 }
```
````

**Migration:** Update your API client to access `users` instead of `data`.

````

## Automation Tools

### Using conventional-changelog
```bash
npm install -g conventional-changelog-cli

# Generate changelog
conventional-changelog -p angular -i CHANGELOG.md -s

# Generate for specific version
conventional-changelog -p angular -i CHANGELOG.md -s -r 0
````

### Using git-cliff

```bash
# Install git-cliff
cargo install git-cliff

# Generate changelog
git-cliff --tag v2.1.0 > CHANGELOG.md

# Generate release notes
git-cliff --tag v2.1.0 --unreleased
```

### GitHub Release Script

```bash
#!/bin/bash
# scripts/release.sh

VERSION=$1
PREVIOUS_TAG=$(git describe --tags --abbrev=0)

# Generate release notes
gh release create "$VERSION" \
  --title "Release $VERSION" \
  --notes "$(git log $PREVIOUS_TAG..HEAD --pretty=format:'- %s')"
```

## User-Facing vs Developer-Facing

### User-Facing (Release Notes)

- Focus on benefits and features
- Less technical jargon
- Include screenshots/demos
- Highlight user experience improvements
- Provide upgrade instructions

### Developer-Facing (Changelog)

- Technical details
- API changes
- Breaking changes with migration guides
- Dependencies updates
- Internal refactorings

## Templates by Project Type

### Library/Package

Focus on: API changes, breaking changes, new methods

### Application

Focus on: New features, bug fixes, UI improvements

### CLI Tool

Focus on: New commands, flag changes, behavior changes

### API Service

Focus on: Endpoint changes, performance, security

## Best Practices

1. **Be specific**: "Fixed login bug" → "Fixed session timeout on mobile"
2. **Link issues**: Reference GitHub issues (#123)
3. **Credit contributors**: Acknowledge work
4. **Highlight impact**: Mark breaking changes clearly
5. **Group logically**: By type, not chronologically
6. **Update regularly**: With each release
7. **Follow conventions**: Keep a Changelog format
8. **Semantic versioning**: Use correctly

## Changelog Entry Examples

### Good Examples

```markdown
### Added

- OAuth2 authentication support (#456) - @alice
- Export data in CSV format with custom column selection (#501)

### Fixed

- Resolved memory leak in WebSocket connections affecting long-running sessions (#489)
- Fixed race condition in concurrent API requests that caused data inconsistency (#503)
```

### Bad Examples

```markdown
### Added

- Added stuff
- New feature

### Fixed

- Fixed bug
- Updates
```

## Version Suggestion Algorithm

```
If breaking changes detected:
  MAJOR++, MINOR=0, PATCH=0
Else if new features:
  MINOR++, PATCH=0
Else if only fixes:
  PATCH++
```

## Release Checklist

Before publishing release:

- [ ] Review all commits since last release
- [ ] Identify breaking changes
- [ ] Categorize changes properly
- [ ] Update CHANGELOG.md
- [ ] Write release notes
- [ ] Update version in package.json/pyproject.toml
- [ ] Create git tag
- [ ] Push tag to trigger CI/CD
- [ ] Publish to package registry (npm, PyPI, etc.)
- [ ] Create GitHub release with notes
- [ ] Announce on relevant channels

## Output Checklist

Every changelog generation should provide:

- [ ] Formatted CHANGELOG.md following Keep a Changelog
- [ ] Release notes draft (user-friendly)
- [ ] Semantic version suggestion (X.Y.Z)
- [ ] Breaking changes clearly marked
- [ ] Migration guide for breaking changes
- [ ] Git tag command to run
- [ ] Links to compare view