topics: add a config to reject draft changeset without topic on a server This patch adds a new config option experimental.topic-mode.server which if sets to True, the server won't accept any draft changeset without topic on it. In case both `experimental.topic-mode.server` and `experimental.topic.publish-bare-branch` are set to True, the enforce-topic one is respected. Tests are added for it. The CHANGELOG file is also updated mentioning about the config option.

#!/bin/sh
. $TESTDIR/testlib/pythonpath.sh

# This file holds logic that is used in many tests.
# It can be called in a test like this:
#  $ . "$TESTDIR/testlib/topic_setup.sh"

# Enable obsolete markers and enable extensions
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers,exchange

[extensions]
rebase=
topic=
EOF