def repo
      @repo = nil if repository_path != @repo.source unless @repo.nil?
      @repo = nil if cache != @repo.cache unless @repo.nil?
      @repo ||= Repo.new.tap do |r|
        r.cache = cache
        r.source = repository_path
      end
    end
def repo
      @repo = nil if repository_path != @repo.source unless @repo.nil?
      @repo = nil if cache != @repo.cache unless @repo.nil?
      @repo ||= Repo.new.tap do |r|
        r.cache = cache
        r.source = repository_path
      end
    end
The corresponding {Repo} for this external.