# File lib/bundler/plugin/api/source.rb, line 188
        def cache(spec, custom_path = nil)
          new_cache_path = app_cache_path(custom_path)

          FileUtils.rm_rf(new_cache_path)
          FileUtils.cp_r(install_path, new_cache_path)
          FileUtils.touch(app_cache_path.join(".bundlecache"))
        end