anchor.diff:  {
       "_index" : "twitter",
       "_type" : "tweet",
  -    "_id" : "1", 
  +    "_id" : "1",
  +    "_version" : 1,
       "found": true,
       "_source" : {
           "user" : "kimchy",
  
positive.code: }
  --------------------------------------------------
  
  The above result includes the `_index`, `_type`, and `_id` of the
  document we wish to retrieve, including the actual source of the
  document that was indexed if it could be found (as indicated by the
  `found` field in the response).
  
  The API also allows to check for the existence of a document using
  `HEAD`, for example:
  
  [source,js]
  --------------------------------------------------
  curl -I 'http://localhost:9200/twitter/tweet/1'
  --------------------------------------------------
  
  [float]
  
negative.code: 
  [source,js]
  --------------------------------------------------
  curl -XHEAD -i 'http://localhost:9200/twitter/tweet/1/_source'
  --------------------------------------------------
  
  [float]
  