参考文献
標準・仕様（一次情報）
- RFC 2119: Key words for use in RFCs to Indicate Requirement Levels
- RFC 8174: Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words
- RFC 3339: Date and Time on the Internet: Timestamps
- Semantic Versioning 2.0.0
- Keep a Changelog
Git / GitHub（一次情報）
- Git documentation
- GitHub Docs: Searching on GitHub
- GitHub Docs: About code search
- GitHub Docs: About pull requests