The official way of creating a private fork by duplicating the repo is documented here: help.github.com/articles/duplicating-a-repository/. It also includes a description of what to do if the repository contains Git Large File Storage objects.
We assume the following:
- Old or original repo is:
git@github.com:<user>/<old-repo>.git - New mirror will be:
git@github.com:<your_username>/mirror.git
For this, the commands are:
- Create a bare clone of the repository. (This is temporary and will be removed so just do it wherever.)