Off-line deverloper workflow?

Hi,

I have a colleague who has to left our office for three month, but still need to work on the project which is hosted on our in-office git repository. Problem is that our company has firewall, it's not possible or not allowed to access the company LAN outside the building. So I want to ask you expert, can you suggest a best practice of git workflow that suitable to my situation?

Thanks in advance.

-woody