title: Make logstash input file configurable
body: <p>I have a logstash agent running well :
  my config file contains an input file with the path to my folder and it send all the data to my elasticsearch database.</p>
  
  <p>But I would like to make my agent more "advanced". I would like to have a external config file or anything else, where you can specify a path or a list of paths of the logs folders you want to parse, and logstash parse it automatically when it runs.</p>
  
  <p>Basically, is it possible to have a config like this:</p>
  
  <pre><code>input
  {
    path=&gt;external parameter given by the user (example : "c:/users/xxxx/*.log")
  }
  </code></pre>
  
  <p>The goal of this is to don't have to write manually by opening the config file an new input file with the recquired path.</p>