+ if not user
+ # Check for permission to log in to an existing User record with
+ # a different identity_url
+ Link.where(link_class: 'permission',
+ name: 'can_login',
+ tail_kind: 'email',
+ tail_uuid: omniauth['info']['email'],
+ head_kind: 'arvados#user').each do |link|
+ if prefix = link.properties['identity_url_prefix']
+ if prefix == omniauth['info']['identity_url'][0..prefix.size-1]
+ user = User.find_by_uuid(link.head_uuid)
+ break if user
+ end
+ end
+ end
+ end