Fix pre-release version check.

Author: nicfit

Makefile

@@ -127,7 +127,7 @@ pre-release: lint test changelog requirements
 	@echo "RELEASE_TAG: $(RELEASE_TAG)"
 	@echo "RELEASE_NAME: $(RELEASE_NAME)"
 	check-manifest
-	@if git tag -l | grep ${RELEASE_TAG} > /dev/null; then \
+	@if git tag -l | grep -E '^$(RELEASE_TAG)$$' > /dev/null; then \
         echo "Version tag '${RELEASE_TAG}' already exists!"; \
         false; \
     fi

cookiecutter/{{cookiecutter.project_name}}/Makefile

@@ -125,7 +125,7 @@ pre-release: lint test changelog requirements
 	@echo "RELEASE_TAG: $(RELEASE_TAG)"
 	@echo "RELEASE_NAME: $(RELEASE_NAME)"
 	check-manifest
-	@if git tag -l | grep ${RELEASE_TAG} > /dev/null; then \
+	@if git tag -l | grep -E '^$(RELEASE_TAG)$$' > /dev/null; then \
         echo "Version tag '${RELEASE_TAG}' already exists!"; \
         false; \
     fi