Dropbox: calculate a directory hash that includes every recursive subfolder

dropbox_entry_recursive_hash.rb

module Dropbox
  class Entry
    def recursive_hash
      return metadata.hash unless metadata.is_dir
      
      recursive_hashes = 
        list.select{ |e| e.is_dir }.map do |e|
          @session.entry( e.path ).recursive_hash
        end
      
      recursive_hashes << metadata.hash
      recursive_hashes.sort!
              
      Digest::MD5.hexdigest( recursive_hashes.join )
    end
  end
end

# session.entry( '/my_dir' ).recursive_path # => "742dcd2b0ea021eaa36d35fd92ddecea"