anchor.diff:  
   [[rollover-index-specify-index-ex]]
   ===== Specify a target index name
  -
  -If the name of the existing index ends with `-` and a number -- e.g.
  -`logs-000001` -- then the name of the new index will follow the same pattern,
  -incrementing the number (`logs-000002`). The number is zero-padded with a length
  -of 6, regardless of the old index name.
  +If the rollover target is a data stream, you cannot specify a target index
  +name. The new index name will always be in the form `<rollover-target>-000001`
  +where the zero-padded number of length 6 is the generation of the data stream.
  +
  +If the rollover target is an index alias and the name of the existing index ends
  +with `-` and a number -- e.g. `logs-000001` -- then the name of the new index will
  +follow the same pattern, incrementing the number (`logs-000002`). The number is
  +zero-padded with a length of 6, regardless of the old index name.
   
   If the old name doesn't match this pattern then you must specify the name for
   the new index as follows:
  
positive.code: `conditions`::
  +
  --
  (Required, object)
  Set of conditions the index alias's existing index must met to roll over.
  
  Parameters include:
  
  
negative.code: [[rollover-index-api-path-params]]
  ==== {api-path-parms-title}
  
  `<rollover-target>`::
  (Required*, string)
  Name of the existing index alias or data stream on which to
  perform the rollover.
  
  
  `<target-index>`::
  