[stable/elasticsearch] add readme for upgrading to es 7; bump to vers…

…ion 6.8

Signed-off-by: Tetiana Kravchenko <tetiana.kravchenko@commercetools.de>

stable/elasticsearch/Chart.yaml

@@ -2,7 +2,7 @@ apiVersion: v1
 name: elasticsearch
 home: https://www.elastic.co/products/elasticsearch
 version: 1.29.0
-appVersion: 7.1.1
+appVersion: 6.8.0
 description: Flexible and powerful open source, distributed real-time search and analytics
   engine.
 icon: https://static-www.elastic.co/assets/blteb1c97719574938d/logo-elastic-elasticsearch-lt.svg

stable/elasticsearch/README.md

@@ -8,6 +8,9 @@ If you are currently using an earlier version of this Chart you will need to red
 If you are upgrading to Elasticsearch 6 from the 5.5 version used in this chart before, please note that your cluster needs to do a full cluster restart.
 The simplest way to do that is to delete the installation (keep the PVs) and install this chart again with the new version.
 If you want to avoid doing that upgrade to Elasticsearch 5.6 first before moving on to Elasticsearch 6.0.
+If you are upgrading to Elasticsearch 7 from the versions previous to 6.8 version, please note that your cluster needs to do a full cluster restart.
+The simplest way to do that is to delete the installation (keep the PVs) and install this chart again with the new version.
+If you want to avoid doing that upgrade to Elasticsearch 6.8 first before moving on to Elasticsearch 7.1.
 
 ## Prerequisites Details
 

stable/elasticsearch/values.yaml

@@ -1,7 +1,7 @@
 # Default values for elasticsearch.
 # This is a YAML-formatted file.
 # Declare variables to be passed into your templates.
-appVersion: "7.1.1"
+appVersion: "6.8.0"
 
 ## Define serviceAccount names for components. Defaults to component's fully qualified name.
 ##
@@ -42,7 +42,7 @@ securityContext:
 
 image:
   repository: "docker.elastic.co/elasticsearch/elasticsearch-oss"
-  tag: "7.1.1"
+  tag: "6.8.0"
   pullPolicy: "IfNotPresent"
   # If specified, use these secrets to access the image
   # pullSecrets: