I'm looking for somekind of version control system where I can create a repository for my project, like SVN for example, but with the abillity to define which portion of the source some user will be able to see and commit changes. If possible, that the user can run a local copy of the project, but without seeing the complete source.
I have a closed-source project and I want to add more developers into it, but I do not want them to see some parts of the source right now, and I don't know which system is better for me.
I already searched for Git, Bitbucket, Assembla (currently using this one), SourceForge, and Google Code, but I think none of them has the feature I am looking for.