README.md in elasticsearch-extensions-0.0.19 vs README.md in elasticsearch-extensions-0.0.20

@@ -88,9 +88,12 @@
     TEST_CLUSTER_PORT=9350 \
     TEST_CLUSTER_NODES=3 \
     TEST_CLUSTER_NAME=my_testing_cluster \
     ruby -r elasticsearch -e "require 'elasticsearch/extensions/test/cluster'; Elasticsearch::Extensions::Test::Cluster.start"
 
+To prevent deleting data and configurations when the cluster is started, for example in a development environment,
+use the `clear_cluster: false` option or the `TEST_CLUSTER_CLEAR=false` environment variable.
+
 [Full documentation](http://rubydoc.info/gems/elasticsearch-extensions/Elasticsearch/Extensions/Test/Cluster)
 
 ### Test::StartupShutdown
 
 Allows to register `startup` and `shutdown` hooks for Test::Unit, similarly to RSpec's `before(:all)`,