RS OAuth pre-fills username for login

app/controllers/rs/oauth_controller.rb

@@ -1,5 +1,5 @@
 class Rs::OauthController < ApplicationController
-  before_action :require_user_signed_in
+  before_action :require_signed_in_with_username
 
   def new
     username, org  = params[:useraddress].split("@")
@@ -97,6 +97,13 @@ class Rs::OauthController < ApplicationController
 
   private
 
+  def require_signed_in_with_username
+    unless user_signed_in?
+      username, org = params[:useraddress].split("@")
+      redirect_to new_user_session_path(cn: username, ou: org)
+    end
+  end
+
   def app_auth_url(auth)
     url = "#{auth.url}#remotestorage=#{current_user.address}"
     url += "&access_token=#{auth.token}"