Rework Makefile targets

`make docker` is now `make local`, and builds for local dev.

`make docker push` is now `make release`; it requires a VERSION in the
environment, and it builds, tags, and pushed imges.

Makefile

@@ -1,27 +1,39 @@
-VERSION := 1.3
 CPPFLAGS += -DVERSION=\"$(VERSION)\"
 
 default: netip
 all: netip fuzzy tester
 
-docker:
+local:
 	docker build \
-	  --build-arg VERSION="$(VERSION)" \
 	  --build-arg BUILD_DATE="$(shell date -u --iso-8601)" \
 	  --build-arg VCS_REF="$(shell git rev-parse --short HEAD)" \
 	  . -t huntprod/netip.cc:latest
 
 	docker build -f Dockerfile.web \
-	  --build-arg VERSION="$(VERSION)" \
 	  --build-arg BUILD_DATE="$(shell date -u --iso-8601)" \
 	  --build-arg VCS_REF="$(shell git rev-parse --short HEAD)" \
 	  . -t huntprod/www.netip.cc:latest
 
-push:
+release:
+	@echo "Checking that VERSION was defined in the calling environment"
+	@test -n "$(VERSION)"
+	@echo "OK.  VERSION=$(VERSION)"
+	docker build \
+	  --build-arg VERSION="$(VERSION)" \
+	  --build-arg BUILD_DATE="$(shell date -u --iso-8601)" \
+	  --build-arg VCS_REF="$(shell git rev-parse --short HEAD)" \
+	  . -t huntprod/netip.cc:latest
+
 	docker tag huntprod/netip.cc:latest huntprod/netip.cc:$(VERSION)
 	docker push huntprod/netip.cc:latest
 	docker push huntprod/netip.cc:$(VERSION)
 
+	docker build -f Dockerfile.web \
+	  --build-arg VERSION="$(VERSION)" \
+	  --build-arg BUILD_DATE="$(shell date -u --iso-8601)" \
+	  --build-arg VCS_REF="$(shell git rev-parse --short HEAD)" \
+	  . -t huntprod/www.netip.cc:latest
+
 	docker tag huntprod/www.netip.cc:latest huntprod/www.netip.cc:$(VERSION)
 	docker push huntprod/www.netip.cc:latest
 	docker push huntprod/www.netip.cc:$(VERSION)