How to give partial access to a project?

Question

GitHub

How in large projects provide partial access to developers.
After all, no one gives access to the entire project to each developer, for security reasons and to avoid draining some technologies. And how can you grant access only to certain files, or even pieces of code?

Answer 1

Large commercial projects have their own git
For example https://m.habr.com/ru/company/ruvds/blog/359216/

Answer 2

Do you invent some technologies that are not subject to drain? It would be interesting to see, if not the algorithm, then at least in what area. Everyone is now on the contrary on the path of the open source code.

Answer 3

Make multiple repositories with different access rights.