There are some possibly related things out there, such as nbgitpuller, which lets you “distribute content in a git repository to your students by having them click a simple link”. So this could be used to pull files into a notebook environment.
There’s also @manics’ jupyter-notebookparams that “takes query parameters from a url to update a parameter cell of a jupyter notebook”. So you can use that to pass a reference into a notebook.
See also this related discussion thread: Pass parameters to a notebook on jupyterhub/binderhub
Things like tljh-repo2docker and yuvipanda/repo2dockerspawner or ideonate/repo2dockerspawner also provide repo2docker spawners that let you build and spawn environments in JupyterHub from a Github or other archive repo.