1. dpkg-mergechangelogs - Debian changelog files
2. composer - composer.json / composer.lock files
3. nbdime - Jupyter notebooks
4. git-json-merge - Generic JSON merge
5. git-po-merge - GNU gettext po files (a wrapper around msgmerge)
6. pom-merge-driver - Maven POM files
7. git-merge-changelog - GNU ChangeLog files
8. npm-merge-driver - NPM package-lock.json files
9. git-lfs-merge-driver - Git LFS files
10. org-merge-driver - Emacs Org Mode
11. spork - Java files
12. jdime - Java files
13. FSTmerge / s3m - Java files
14. jsFSTMerge - Javascript files
15. DMFO - Word .doc and .docx files
16. Unity SmartMerge - Unity scene and prefab files

1. Defining a custom merge driver in the official docs

1. smartmerge
2. Mergiraf - Java, Rust, Go, Javascript, C, C++, C#, JSON, HTML, XML, YAML and growing
3. Plume-lib merging - Version numbers; Java imports and annotations; and more

License

This awesome list is licensed under the CC-0 license.