anchor.diff:  `discovery-file` directory to the `config` folder, and a default `unicast_hosts.txt`
   file that must be edited with the correct unicast hosts list before starting the node.
   
  +This plugin can be downloaded for <<plugin-management-custom-url,offline install>> from
  +{plugin_url}/discovery-file/discovery-file-{version}.zip.
  +
  +
   [[discovery-file-remove]]
   [float]
   ==== Removal
  
positive.code: ----
  
  This plugin simply provides a facility to supply the unicast hosts list for
  zen discovery through an external file that can be updated at any time by a side process.  
  
  For example, this gives a convenient mechanism for an Elasticsearch instance 
  that is  run in docker containers to be dynamically supplied a list of IP 
  addresses to connect to for zen discovery when those IP addresses may not be 
  known at node startup.  
  
  Note that the file-based discovery plugin is meant to augment the unicast
  hosts list in `elasticsearch.yml` (if specified), not replace it.  Therefore,
  
negative.code: [float]
  ==== Using the file-based discovery plugin
  
  The file-based discovery plugin provides the ability to specify the
  unicast hosts list through a simple `unicast_hosts.txt` file that can
  be dynamically updated at any time. To enable, add the following in `elasticsearch.yml`:
  
  