Put doc/ back on -trunk too

doc/sphinx/whats-new/changes-trunk.rst

+.. _whatsnew_changes_CURRENT:
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Changes in Varnish **${NEXT_RELEASE}**
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+For information about updating your current Varnish deployment to the
+new version, see :ref:`whatsnew_upgrading_CURRENT`.
+
+A more detailed and technical account of changes in Varnish, with
+links to issues that have been fixed and pull requests that have been
+merged, may be found in the `change log`_.
+
+.. _change log: https://github.com/varnishcache/varnish-cache/blob/master/doc/changes.rst
+
+*eof*

doc/sphinx/whats-new/index.rst

@@ -13,6 +13,19 @@ This section describes the changes and improvements between different
 versions of Varnish, and what upgrading between the different versions
 entail.
 
+Varnish **$NEXT_RELEASE**
+-------------------------
+
+**Note: These are working documents for a future release, with running
+updates for changes in the development branch. For changes in the
+released versions of Varnish, see the chapters listed below.**
+
+.. toctree::
+   :maxdepth: 2
+ 
+   changes-trunk
+   upgrading-trunk
+
 Varnish 7.3
 -----------
 

doc/sphinx/whats-new/upgrading-trunk.rst

+**Note: This is a working document for a future release, with running
+updates for changes in the development branch. For changes in the
+released versions of Varnish, see:** :ref:`whats-new-index`
+ 
+.. _whatsnew_upgrading_CURRENT:
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Upgrading to Varnish **$NEXT_RELEASE**
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+**XXX: how to upgrade from previous deployments to this
+version. Limited to work that has to be done for an upgrade, new
+features are listed in "Changes". Explicitly mention what does *not*
+have to be changed, especially in VCL. May include, but is not limited
+to:**
+
+*eof*