I don't think so, though maybe I didn't explain myself correctly. You can link to a relative package wheel I think, but not to a package repo. So if you have a repo, with your main package in ./src, and you vendor or need a package from another subfolder (let's say ./vendored/freetype) , you can't actually do it in a way that won't break the moment you share your package. You can't put ./vendored/freetype in your requirements.txt, it just fails.
That means you either need to use pypi or do an extremely messy hack that involves adding the vendored package as a sub package to your main source, and then do some importlib black magic to make sure that everything uses said package.
https://github.com/pypa/pip/issues/6658
https://discuss.python.org/t/what-is-the-correct-interpretat...