Restricting users to a branch on GITHUB

Question

We have a situation where we need external contractors to do some work on a project but would like to restrict them to a certain branch on our (private) repository and manage the merging of this branch into the release branches ourselves. Is there a way of restricting users to a single branch of a repository?

Answer 1

Ask that person to fork the project and submit pull request when merging.

Note that their fork will be private, even if their github account is on a free plan.