[Compose] Mount git log head

docker-compose.yml

@@ -110,6 +110,7 @@ services:
       depends_on:
         - redis-mailcow
       volumes:
+        - ./.git/logs/HEAD:/git_head
         - ./data/web:/web:rw
         - ./data/conf/rspamd/dynmaps:/dynmaps:ro
         - rspamd-sock:/rspamd-sock