How to grant access only to a specific folder(s), files in web development?

Question

GitHub

I have a phpstorm project. How to give access to another programmer only to a certain folder (folders), files (file) in web development? If you add a project to github, then there you can configure access only to the entire repository. How can I do this so that edits can be tracked? Maybe there are other options that are simpler?
ps is one of the purposes, among other things, to prevent another programmer from seeing the source code of other files, not only from editing them.