add task for publishing "latest" images

Author: virtualstaticvoid

.github/workflows/build-publish.yml

@@ -9,6 +9,7 @@ on:
 env:
   REGISTRY: ghcr.io
   IMAGE_NAME: ghcr.io/${{ github.repository }}
+  LATEST_VERSION: 4.4.2
 
 jobs:
   build:
@@ -42,3 +43,7 @@ jobs:
       - name: Publish images
         if: github.event_name != 'pull_request'
         run: make --no-builtin-rules push R_VERSION=${{ matrix.r_version }}
+
+      - name: Publish latest images
+        if: github.event_name != 'pull_request' && '${{ matrix.r_version }}' == '${{ env.LATEST_VERSION }}'
+        run: make --no-builtin-rules push-latest R_VERSION=${{ matrix.r_version }}

Makefile

@@ -10,7 +10,6 @@ export
 
 .PHONY: build
 build:
-
 	# "base" image
 	docker build \
 		--pull \
@@ -48,7 +47,6 @@ build:
 
 .PHONY: test
 test:
-
 	# smoke test images, before running units
 	docker run --tty --rm $(IMAGE_TAG) R --no-save -e "capabilities()"
 	docker run --tty --rm $(IMAGE_TAG)-build R --no-save -e "capabilities()"
@@ -60,18 +58,19 @@ test:
 
 .PHONY: push
 push:
-
-	docker push $(IMAGE_NAME):latest
+	# image names contain R version
 	docker push $(IMAGE_TAG)
-
-	docker push $(IMAGE_NAME):build
 	docker push $(IMAGE_TAG)-build
-
-	docker push $(IMAGE_NAME):shiny
 	docker push $(IMAGE_TAG)-shiny
+	docker push $(IMAGE_TAG)-plumber
 
+.PHONY: push-latest
+push-latest:
+	# images labelled as "latest"
+	docker push $(IMAGE_NAME):latest
+	docker push $(IMAGE_NAME):build
+	docker push $(IMAGE_NAME):shiny
 	docker push $(IMAGE_NAME):plumber
-	docker push $(IMAGE_TAG)-plumber
 
 # adapted from https://stackoverflow.com/a/48782113/30521
 env-%: