How to merge two indices in different ES instance into one?

We have a elasticsearch cluster and just one node.

But this day, one guy shutdown this cluster and copy ES dir to another place. Then he run a new elastic instance. We found it and shut down the new instance. Then start the older one.

So now we have:

 elasticsearch-1.7.0/data/elasticsearch_dc_001/nodes/0/indices/logstash-2015.11.10/
 elasticsearch-1.7.0_new/data/elasticsearch_dc_001/nodes/0/indices/logstash-2015.11.10/

So our (2015.11.10) logstash data are in two indices. How to merge the index of elasticsearch-1.7.0_new to elasticsearch-1.7.0?

You could start 2 clusters and read with logstash from one to the other. Aka reindex.

Thanks, I will try it later!