Is it possible in git to have sub project folder permission managment -

I'm new to Git, so it's really a newbie question.

Is it possible to use a permission model on the Git folder? Therefore, there may be a separate sub-projects, and others can invite only to access some folder parts of the project. In this case I am using my personal repo; When a setup is Sourcetree (I'm using the SourceTree client)

Setup within a repository Is not possible to do. The git was not built for closed source software, if I were you, I would split the project into private and public parts (no problem with the directory structure) and will be included in two parts using some build tools.

You have not mentioned the programming language. It will depend on the language, in addition you can also look in the GIT sub-module, although I would recommend the above mentioned approach.