add default tag

check.sh

@@ -36,10 +36,20 @@ TARGET_TAG=$(echo "${TARGET}" | sed 's/[^:]*://')
 BASE_REPO=$(echo "${BASE}" | sed 's/:.*//')
 TARGET_REPO=$(echo "${TARGET}" | sed 's/:.*//') 
 
+# if no tag is give default to latest
+if [ -z "${BASE_TAG}" ]; then
+  BASE_TAG="latest"
+fi
+
+if [ -z "${TARGET_TAG}" ]; then
+  TARGET_TAG="latest"
+fi
+
+
+# build the url to the repo
 BASE_URL="https://hub.docker.com/v2/repositories/${BASE_REPO}/tags/${BASE_TAG}"
 TARGET_URL="https://hub.docker.com/v2/repositories/${TARGET_REPO}/tags/${TARGET_TAG}"
 
-
 # login if credentias are passed
 HEADER=""
 if [ -n "${DOCKER_USERNAME}" ] && [ -n "${DOCKER_PASSWORD}" ]; then