A Devise user#update_with_password which only requires the current password if changing the password

user.rb

def update_with_password(params={})
  result = nil
  current_password = params.delete(:current_password)

  if params[:password].blank?
    params.delete(:password)
    params.delete(:password_confirmation) if params[:password_confirmation].blank?
    result = self.update_without_password(params)
  else
    result = if valid_password?(current_password)
      update_attributes(params)
    else
      self.errors.add(:current_password, current_password.blank? ? :blank : :invalid)
      self.attributes = params
      false
    end
    clean_up_passwords
  end
  result
end