+DOCKER_VER := $(shell [[ "$$(docker version --format '{{.Client.Version}}')" =~ ([0-9]+)\.([0-9]+) ]] && echo $$(( $${BASH_REMATCH[1]} * 100 + $${BASH_REMATCH[2]} )))
+
+# Don't use -f flag when docker is newer than 1.9
+# https://docs.docker.com/engine/deprecated/#/f-flag-on-docker-tag
+ifeq ($(shell echo "$(DOCKER_VER)>109" | bc), 1)
+ tag_flags :=
+else
+ tag_flags := -f
+endif