[hibernate-dev] Pleas help with GITHub, how to get new branches into personal fork?

Hello hibernate developers, I want to open a JIRA-Issue and as always I like to provide an according test-case in form of a pull-request. I already created pull-requests in past, but now I need to update/align my fork of hibernate-orm with branch 4.2 which at the time of fork-creation did not exist yet. How to do that without destroying my fork first? It seems that GitHub does allow maximal one fork per repository. I tried almost everything imaginable without success. If someone could give me an advice please.. thanks Guenther Demetz