Most version control tools / systems provide mechanics with the ability to add links to other repositories in your repository.
Thus, you can save your repository in its pure form from files of other repositories, but still you can just point to the correct library and version.
In Git, its called submodules. In SVN it is called external.
In the end, you will need to decide whether you want to include the files in your repo so that others cannot check other repositories as well, even if the links (submodule / external) make it quite simple. Id prefers pure repo, although it references other repositories, if available. It will also simplify the maintenance and updating of these libraries.
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