Make oauth works for google oauth too

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

CHANGELOG

@@ -8,6 +8,7 @@ v 6.8.0
   - Create branches via API (sponsored by O'Reilly Media)
   - Changed permission of gitlab-satellites directory not to be world accessible
   - Protected branch does not allow force push
+  - Allow oauth signup without email for twitter and github
 
 v 6.7.3
   - Fix the merge notification email not being sent (Pierre de La Morinerie)

lib/gitlab/oauth/user.rb

@@ -30,11 +30,17 @@ module Gitlab
           user = model.build_user(opts, as: :admin)
           user.skip_confirmation!
 
+          # Services like twitter and github does not return email via oauth
+          # In this case we generate temporary email and force user to fill it later
           if user.email.blank?
             user.generate_tmp_oauth_email
-          end
-
             user.save!(validate: false)
+          else
+            # Google oauth returns email but dont return nickname
+            # So we use part of email as username for new user
+            user.username = email.match(/^[^@]*/)[0]
+            user.save
+          end
 
           log.info "(OAuth) Creating user #{email} from login with extern_uid => #{uid}"