anchor.diff:  only those columns to appear. For example:
   
   [source,console]
  ---------------------------------------------------
  -GET /_cat/nodes?h=ip,port,heapPercent,name
  ---------------------------------------------------
  +----
  +GET _cat/nodes?h=ip,port,heapPercent,name
  +----
   
   Responds with:
   
   [source,txt]
  ---------------------------------------------------
  +----
   127.0.0.1 9300 27 sLBaIGK
  ---------------------------------------------------
  +----
   // TESTRESPONSE[s/9300 27 sLBaIGK/\\d+ \\d+ .+/ non_json]
   
   You can also request multiple columns using simple wildcards like
  
positive.code: . The `v` (verbose) parameter to include column headings in the response.
  
  [source,console]
  --------------------------------------------------
  GET /_cat/indices?bytes=b&s=store.size:desc,index:asc&v=true
  --------------------------------------------------
  // TEST[setup:my_index_huge]
  // TEST[s/^/PUT my-index-000002\n{"settings": {"number_of_replicas": 0}}\n/]
  
  The API returns the following response:
  
  [source,txt]
  --------------------------------------------------
  health status index            uuid                   pri rep docs.count docs.deleted store.size pri.store.size
  yellow open   my-index-000001  u8FNjxh8Rfy_awN11oDKYQ   1   1       1200            0      72171         72171
  green  open   my-index-000002  nYFWZEO7TUiOjLQXBaYJpA   1   0          0            0        230          230
  --------------------------------------------------
  // TESTRESPONSE[s/72171|230/\\d+/]
  // TESTRESPONSE[s/u8FNjxh8Rfy_awN11oDKYQ|nYFWZEO7TUiOjLQXBaYJpA/.+/ non_json]
  
  
negative.code: ==== Response as text, json, smile, yaml or cbor
  
  [source,sh]
  ----
  % curl 'localhost:9200/_cat/indices?format=json&pretty'
  [
    {
  