Gem::RemoteFetcher#cache_update_path

# File tmp/rubies/ruby-3.4.1/lib/rubygems/remote_fetcher.rb, line 286
def cache_update_path(uri, path = nil, update = true)
  mtime = begin
            path && File.stat(path).mtime
          rescue StandardError
            nil
          end

  data = fetch_path(uri, mtime)

  if data.nil? # indicates the server returned 304 Not Modified
    return Gem.read_binary(path)
  end

  if update && path
    Gem.write_binary(path, data)
  end

  data
end