zquestz/omniauth-google-oauth2 — pull request #29 by bradleybuda (2012-06-19 00:37:41+00:00)
Title: Add the "hd" (Hosted Domain) parameter

Forces a user to log in to a particular Google Apps domain, instead of just any Google Account. This is pretty much undocumented, but it works; see https://groups.google.com/d/msg/oauth2-dev/SRStIuewiws/sQ87tPyHfYIJ