Git subtree allows incorporating external repositories into your project as subdirectories without the complexity of submodules. As the creator of CoreUI with over 25 years of version control experience since 2000, I’ve used subtree merging to integrate third-party libraries while maintaining full control over the code. The standard approach adds a remote for the external repository, then uses git subtree to merge it into a specific directory. This provides cleaner workflows than submodules for vendoring dependencies.