class Devise::RegistrationsController

def update

the current user in place.
We need to use a copy of the resource because we don't want to change
PUT /resource 
def update
  self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
  prev_unconfirmed_email = resource.unconfirmed_email if resource.respond_to?(:unconfirmed_email)
  if resource.update_with_password(resource_params)
    if is_navigational_format?
      flash_key = update_needs_confirmation?(resource, prev_unconfirmed_email) ?
        :update_needs_confirmation : :updated
      set_flash_message :notice, flash_key
    end
    sign_in resource_name, resource, :bypass => true
    respond_with resource, :location => after_update_path_for(resource)
  else
    clean_up_passwords resource
    respond_with resource
  end
end