# File lib/chef/cookbook_version.rb, line 244
    def self.clear_obsoleted_cookbooks(cookbook_hash)
      # Remove all cookbooks no longer relevant to this node
      cache.find(File.join(%w{cookbooks ** *})).each do |cache_file|
        cache_file =~ /^cookbooks\/([^\/]+)\//
        unless cookbook_hash.has_key?($1)
          Chef::Log.info("Removing #{cache_file} from the cache; its cookbook is no longer needed on this client.")
          cache.delete(cache_file)
        end
      end
    end