Bug 1867119: Add the evolve extension to the updatebot Dockerfile r=freddyb

This is needed so we can use evolve commands like `hg next`
which is needed to submit two patches to phabricator separately.

Differential Revision: https://phabricator.services.mozilla.com/D196727

taskcluster/docker/updatebot/hgrc

@@ -4,4 +4,8 @@ username = Updatebot <updatebot@mozilla.com>
 
 [extensions]
 strip =
-push-to-try = $HOME/.mozbuild/version-control-tools/hgext/push-to-try
+evolve = $HOME/.mozbuild/evolve/hgext3rd/evolve
+push-to-try = $HOME/.mozbuild/version-control-tools/hgext/push-to-try
+
+[experimental]
+evolution=all

taskcluster/docker/updatebot/setup.sh

@@ -5,6 +5,12 @@
 
 set -vex
 
+# Install the evolve extension
+# Mercurial will complain that it can't find the evolve extension - this is
+# because we don't have it yet, and we are asking mercurial to go install it
+# so mercurial can use it.
+hg clone https://repo.mercurial-scm.org/evolve/ "$HOME/.mozbuild/evolve"
+
 # Copy the system known_hosts to the home directory so we have uniformity with Windows
 # and the ssh command will find them in the same place.
 cp /etc/ssh/ssh_known_hosts "$HOME/ssh_known_hosts"