use

# File lib/bundler/index.rb, line 142
    def use(other, override_dupes = false)
      return unless other
      other.each do |s|
        if (dupes = search_by_spec(s)) && !dupes.empty?
          # safe to << since it's a new array when it has contents
          @all_specs[s.name] = dupes << s
          next unless override_dupes
        end
        self << s
      end
      self
    end