Add filter plugins

ansible.cfg

@@ -1,6 +1,7 @@
 [defaults]
-retry_files_enabled = false
+filter_plugins = /var/lib/dokku/plugins/available/ansible-deploy/plays/filter_plugins
 interpreter_python = /usr/bin/python3
+retry_files_enabled = false
 
 [ssh_connection]
 pipelining = true

plays/filter_plugins/update_env.py

@@ -0,0 +1,12 @@
+"""Update config.env filter."""
+
+
+def filter_update_env(config, env):
+    for key, val in env:
+        config["env"][key] = val
+    return config
+
+
+class FilterModule(object):
+    def filters(self):
+        return {"update_env": filter_update_env}