Add Portainer Git directory to env file

docker-compose.yml

@@ -5,7 +5,7 @@ services:
     image: pathogen/threshold
     build: .
     volumes:
-      - .:/code
+      - ${PORTAINER_GIT_DIR}:/code
     ports:
       - "${THRESHOLD_LISTENER_PORT}:${THRESHOLD_LISTENER_PORT}"
       - "${THRESHOLD_RELAY_PORT}:${THRESHOLD_RELAY_PORT}"