The CHANGES file on FTP is not rendered

The CHANGES file is a link to doc/arm/changelog.rst. After !9549 (merged), the doc/arm/changelog.rst file includes versioned changelog files, and if the release job copies it to release tarball, it won't be rendered and will be fairly useless for FTP consumption:

...
Changelog
=========

.. note:: The following list contains detailed information about BIND9's
   development. Regular users should refer to :ref:`Release Notes <relnotes>`
   for changes relevant to them.

.. include:: ../changelog/changelog-9.21.2.rst
.. include:: ../changelog/changelog-9.21.1.rst
.. include:: ../changelog/changelog-9.21.0.rst
.. include:: ../changelog/changelog-history.rst

We either need to render it to TXT or hack it.

The Sphinx Text builder looks like a natural fit, but the problem is Sphinx keeps crunching reference.rst after 10 minutes...

--- a/doc/arm/Makefile.am
+++ b/doc/arm/Makefile.am
@@ -104,7 +104,14 @@ install-epub:
        $(INSTALL) -d $(DESTDIR)/$(docdir)
        $(INSTALL_DATA) $(SPHINXBUILDDIR)/epub/*.epub $(DESTDIR)/$(docdir)/
 
+text:
+       $(AM_V_SPHINX)$(SPHINX_BUILD) -b text -d $(SPHINXBUILDDIR)/.doctrees/text $(ALLSPHINXOPTS) $(SPHINXBUILDDIR)/text
+
+install-text:
+       $(INSTALL) -d $(DESTDIR)/$(docdir)
+       $(INSTALL_DATA) $(SPHINXBUILDDIR)/text/*.txt $(DESTDIR)/$(docdir)/
+
 clean-local:
        -rm -rf $(SPHINXBUILDDIR)
 
-doc-local: html singlehtml epub
+doc-local: html singlehtml epub text

The output of links -dump doc/arm/_build/html/changelog.html looks fine, but starts with a table of contents, so it needs some CLI processing still.

So, I think this is the best we can achieve with 2024 engineering:

(
  cat $(find doc/changelog/changelog-9.*.rst | sort --version-sort --reverse; echo doc/changelog/changelog-history.rst)
) | grep -v '^\.\.' > CHANGES

See the MM discussion.

• Also, some find the line "Changes prior to 9.20.0" confusing and believe it should read "Changes prior to 9.20.1".