class ActiveSupport::EventedFileUpdateChecker::Core

def initialize(files, dirs)
  @files = files.map { |file| Pathname(file).expand_path }.to_set
  @dirs = dirs.each_with_object({}) do |(dir, exts), hash|
    hash[Pathname(dir).expand_path] = Array(exts).map { |ext| ext.to_s.sub(/\A\.?/, ".") }.to_set
  end
  @common_path = common_path(@dirs.keys)
  @dtw = directories_to_watch
  @missing = []
  @updated = Concurrent::AtomicBoolean.new(false)
  @mutex = Mutex.new
  start
  @after_fork = ActiveSupport::ForkTracker.after_fork { start }
end