gitlab-org--gitlab-foss/app/models/protected_tag.rb

class ProtectedTag < ActiveRecord::Base
  include Gitlab::ShellAdapter
  include ProtectedRef

  has_many :push_access_levels, dependent: :destroy

  validates :push_access_levels, length: { is: 1, message: "are restricted to a single instance per protected tag." }

  accepts_nested_attributes_for :push_access_levels
end