chore: align Makefile Docker variables

Author: fxik

Makefile

@@ -1,4 +1,5 @@
-IMAGE_PREFIX ?= dockette
+DOCKER_IMAGE_PREFIX?=dockette
+DOCKER_TAG?=latest
 IMAGES := jdk8 mvn openjdk-mvn openjdk8
 
 .PHONY: build test run $(addprefix build-,$(IMAGES)) $(addprefix test-,$(IMAGES)) $(addprefix run-,$(IMAGES))
@@ -9,37 +10,39 @@ test: $(addprefix test-,$(IMAGES))
 run: run-openjdk8
 
 build-jdk8:
-	docker build -t $(IMAGE_PREFIX)/jdk8:latest jdk8
+	docker build -t ${DOCKER_IMAGE_PREFIX}/jdk8:${DOCKER_TAG} jdk8
 
 build-mvn:
-	docker build -t $(IMAGE_PREFIX)/mvn:latest mvn
+	docker build -t ${DOCKER_IMAGE_PREFIX}/mvn:${DOCKER_TAG} mvn
 
 build-openjdk-mvn:
-	docker build -t $(IMAGE_PREFIX)/openjdk-mvn:latest openjdk-mvn
+	docker build -t ${DOCKER_IMAGE_PREFIX}/openjdk-mvn:${DOCKER_TAG} openjdk-mvn
 
 build-openjdk8:
-	docker build -t $(IMAGE_PREFIX)/openjdk8:latest openjdk8
+	docker build -t ${DOCKER_IMAGE_PREFIX}/openjdk8:${DOCKER_TAG} openjdk8
 
 test-jdk8:
-	docker run --rm $(IMAGE_PREFIX)/jdk8:latest java -version
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/jdk8:${DOCKER_TAG} java -version
 
 test-mvn:
-	docker run --rm $(IMAGE_PREFIX)/mvn:latest sh -lc 'java -version && mvn -version'
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/mvn:${DOCKER_TAG} java -version
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/mvn:${DOCKER_TAG} mvn -version
 
 test-openjdk-mvn:
-	docker run --rm $(IMAGE_PREFIX)/openjdk-mvn:latest sh -lc 'java -version && mvn -version'
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/openjdk-mvn:${DOCKER_TAG} java -version
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/openjdk-mvn:${DOCKER_TAG} mvn -version
 
 test-openjdk8:
-	docker run --rm $(IMAGE_PREFIX)/openjdk8:latest java -version
+	docker run --rm ${DOCKER_IMAGE_PREFIX}/openjdk8:${DOCKER_TAG} java -version
 
 run-jdk8:
-	docker run --rm -it -v $(PWD):/data $(IMAGE_PREFIX)/jdk8:latest java -version
+	docker run --rm -it -v "$${PWD}:/data" ${DOCKER_IMAGE_PREFIX}/jdk8:${DOCKER_TAG} java -version
 
 run-mvn:
-	docker run --rm -it -v $(PWD):/data $(IMAGE_PREFIX)/mvn:latest
+	docker run --rm -it -v "$${PWD}:/data" ${DOCKER_IMAGE_PREFIX}/mvn:${DOCKER_TAG}
 
 run-openjdk-mvn:
-	docker run --rm -it -v $(PWD):/data $(IMAGE_PREFIX)/openjdk-mvn:latest
+	docker run --rm -it -v "$${PWD}:/data" ${DOCKER_IMAGE_PREFIX}/openjdk-mvn:${DOCKER_TAG}
 
 run-openjdk8:
-	docker run --rm -it -v $(PWD):/data $(IMAGE_PREFIX)/openjdk8:latest java -version
+	docker run --rm -it -v "$${PWD}:/data" ${DOCKER_IMAGE_PREFIX}/openjdk8:${DOCKER_TAG} java -version