Update version following 8.0 release.

api_docs/changelog.md

@@ -18,6 +18,11 @@ clients should check the `zulip_feature_level` field, present in the
 /register`](/api/register-queue) responses, to determine the API
 format used by the Zulip server that they are interacting with.
 
+## Changes in Zulip 9.0
+
+Feature levels 238-239 are reserved for future use in 8.x maintenance
+releases.
+
 ## Changes in Zulip 8.0
 
 **Feature level 237**

docs/overview/changelog.md

@@ -1,9 +1,19 @@
 # Version history
 
-This page contains the release history for the Zulip 8.x stable
-release series. See the [current Zulip changelog][latest-changelog]
-for newer release series, or the [commit log][commit-log] for an
-up-to-date list of all changes.
+This page contains the release history for the Zulip server. See also the
+[Zulip release lifecycle](../overview/release-lifecycle.md).
+
+## Zulip 9.x series
+
+### 9.0 -- unreleased
+
+This section is an incomplete draft of the release notes for the next
+major release, and is only updated occasionally. See the [commit
+log][commit-log] for an up-to-date list of all changes.
+
+#### Upgrade notes for 9.0
+
+- None yet.
 
 ## Zulip Server 8.x series
 
@@ -3706,6 +3716,7 @@ _Released 2015-10-19_
 This section links to the upgrade notes from past releases, so you can
 easily read them all when upgrading across multiple releases.
 
+- [Draft upgrade notes for 8.0](#upgrade-notes-for-90)
 - [Upgrade notes for 8.0](#upgrade-notes-for-80)
 - [Upgrade notes for 7.0](#upgrade-notes-for-70)
 - [Upgrade notes for 6.0](#upgrade-notes-for-60)

version.py

@@ -1,6 +1,6 @@
 import os
 
-ZULIP_VERSION = "8.0"
+ZULIP_VERSION = "9.0-dev+git"
 
 # Add information on number of commits and commit hash to version, if available
 zulip_git_version_file = os.path.join(