Upate Gerrit v3.9.0 release notes for rc6

Also add the missing indexing schema upgrades:
- accounts upgraded to v13
- groups upgraded to v10

Change-Id: I91e3ceb77ba649128dc5a7138b3fbf5192c798f8

pages/site/releases/3.9.md

@@ -6,9 +6,9 @@ hide_navtoggle: true
 toc: true
 ---
 
-Download: **[3.9.0](https://gerrit-releases.storage.googleapis.com/gerrit-3.9.0.war)**
+Download: **[3.9.0-rc6](https://gerrit-releases.storage.googleapis.com/gerrit-3.9.0-rc6.war)**
 
-Documentation: **[3.9.0](http://gerrit-documentation.storage.googleapis.com/Documentation/3.9.0/index.html)**
+Documentation: **[3.9.0-rc6](http://gerrit-documentation.storage.googleapis.com/Documentation/3.9.0-rc6/index.html)**
 
 ## Release highlights
 
@@ -123,15 +123,17 @@ and fail to locate changes imported from Gerrit servers with a different server-
 
 This release doesn't contain schema changes.
 
+The `accounts` index version has been increased to version _13_.
 The `changes` index version has been increased to version _85_.
+The `groups` index version has been increased to version _10_.
 The `projects` index version has been increased to version _8_.
 
-### Online index schema upgrade from 3.8
+### Online index schema upgrade from 3.7/3.8
 
-By default, if you're upgrading from 3.8, the index is automatically rebuilt
+By default, if you're upgrading from 3.7/3.8, the index is automatically rebuilt
 upon Gerrit startup after the upgrade.
 
-If you're upgrading from 3.7 or an earlier version, you must use the Offline
+If you're upgrading from 3.6 or an earlier version, you must use the Offline
 upgrade steps below.
 
 ### Offline upgrade
@@ -147,16 +149,15 @@ upgrade steps below.
 
 5. Reindex
 
-* If you are upgrading from a 3.8 version you don't need to run reindex (see
-  `Online index schema upgrade from 3.8` above). If you still want to you will
-  only need to run reindex of `changes`:
+* If you are upgrading from a 3.7/3.8 versions you don't need to run reindex (see
+  `Online index schema upgrade from 3.7/3.8` above). If you still want to you will
+  need to run reindex:
 
     ```sh
-    java -jar gerrit.war reindex --index changes -d site_path
-    java -jar gerrit.war reindex --index projects -d site_path
+    java -jar gerrit.war reindex -d site_path
     ```
 
-* If you are upgrading from a 3.7 version, or an earlier version, you must run a
+* If you are upgrading from a 3.6 or an earlier version, you must run a
   reindex of all indexes:
 
    ```sh
@@ -171,7 +172,7 @@ program for other options.
 
 ### Online upgrade with zero-downtime
 
-Gerrit v3.9.x supports zero-downtime upgrade from Gerrit v3.8.2 or later when
+Gerrit v3.9.x supports zero-downtime upgrade from Gerrit v3.7 or later when
 configured using
 a [high-availability configuration](https://gerrit.googlesource.com/plugins/high-availability/+/refs/heads/master/README.md)
 , and the Git repositories are stored in a shared filesystem such as NFS or
@@ -183,7 +184,7 @@ operation on the GUI or using any API.
 
 The zero-downtime upgrade consists of the following steps:
 
-1. Have Gerrit servers running v3.8.2 or later, in high-availability
+1. Have Gerrit servers running v3.7 or later, in high-availability
    configuration, healthy and able to handle the incoming traffic properly.
 2. Set `gerrit.experimentalRollingUpgrade` to `true` in `gerrit.config` on both
    Gerrit primaries.
@@ -199,16 +200,16 @@ The zero-downtime upgrade consists of the following steps:
 
 ### Downgrade
 
-Downgrade to any Gerrit v3.8.x release is possible, but requires the following
+Downgrade to any Gerrit v3.7/v3.8 release is possible, but requires the following
 manual steps:
 
-1. Shutdown all migrated Gerrit v3.8.x servers
-2. Update the gerrit.war and plugins to the previous v3.8.x version
+1. Shutdown all migrated Gerrit servers
+2. Update the gerrit.war and plugins to the previous v3.7/v3.8 version
 3. Run offline change reindexing using the previous gerrit.war version
 
 ```sh
   java -jar gerrit.war init -d site_path --batch
-  java -jar gerrit.war reindex --index changes -d site_path
+  java -jar gerrit.war reindex -d site_path
 ```
 
 4. Startup Gerrit server