watchr file to auto build my docbook PDF

main.rb

@auto_generated_files = [
                         "xsl/fo.xml"
                         ]

watch("(.*.[xml|xsl])") {|m| rebuild(m[1]) unless @auto_generated_files.include?(m[1]) }

def rebuild(file_change)
  puts "[watchr] Rebuilding because #{file_change} changed"
  system("rake")
  puts "[watchr] Waiting for changes"
end