class Guard::Watcher

• files (Array) -- the changed files
• guard (Guard::Guard) -- the guard which watchers are used

def self.match_files(guard, files)
  guard.watchers.inject([]) do |paths, watcher|
    files.each do |file|
      if matches = watcher.match(file)
        if watcher.action
          result = watcher.call_action(matches)
          if guard.options[:any_return]
            paths << result
          elsif result.respond_to?(:empty?) && !result.empty?
            paths << Array(result)
          end
        else
          paths << matches[0]
        end
      end
    end
    guard.options[:any_return] ? paths : paths.flatten.map { |p| p.to_s }
  end
end