ci: tag eynollah docker image with git tag version if possible, else latest

Makefile

@@ -2,8 +2,7 @@ PYTHON ?= python3
 PIP ?= pip3
 EXTRAS ?=
 
-# DOCKER_BASE_IMAGE = artefakt.dev.sbb.berlin:5000/sbb/ocrd_core:v2.68.0
-DOCKER_BASE_IMAGE ?= docker.io/ocrd/core-cuda-tf2:latest
+DOCKER_BASE_IMAGE ?= docker.io/ocrd/core-cuda-tf2:3.12.2
 DOCKER_TAG ?= ocrd/eynollah
 DOCKER ?= docker
 WGET = wget -O
@@ -120,12 +119,19 @@ coverage:
 	$(MAKE) test PYTHON="coverage run"
 	coverage report -m
 
+# Concatenate docker image names with either the git tag describing current commit or 'latest' and
+# merge list with "-t"
+empty :=
+space := $(empty) $(empty)
+GIT_TAG := $(strip $(shell git describe --tags | grep -x "v[0-9]\+\.[0-9]\+\.[0-9]\+"))
+DOCKER_TAGS = $(subst $(space),$(space)-t$(space),$(DOCKER_TAG:%=$(if $(GIT_TAG),%:$(GIT_TAG),%:latest)))
+
 # Build docker image
 docker:
 	$(DOCKER) build \
 	--build-arg DOCKER_BASE_IMAGE=$(DOCKER_BASE_IMAGE) \
 	--build-arg VCS_REF=$$(git rev-parse --short HEAD) \
 	--build-arg BUILD_DATE=$$(date -u +"%Y-%m-%dT%H:%M:%SZ") \
-	-t $(DOCKER_TAG) .
+	-t $(DOCKER_TAGS) .
 
 .PHONY: models build install install-dev test smoke-test ocrd-test coverage docker help