Try to simplify

Author: coretl

.github/workflows/ci.yml

@@ -1,3 +1,7 @@
+# Written using
+# https://docs.docker.com/build/ci/github-actions/multi-platform/
+# and
+# https://github.com/sredevopsorg/multi-arch-docker-github-workflow/blob/main/.github/workflows/multi-build.yaml
 name: CI
 
 on:
@@ -8,7 +12,12 @@ on:
       - '*'
   pull_request:
 
-# https://docs.docker.com/build/ci/github-actions/multi-platform/
+env:
+  # The name of the Docker image to be built and pushed to GHCR
+  # The image name is derived from the GitHub repository name and the GitHub Container Registry (GHCR) URL.
+  # The image name will be in the format: ghcr.io/<owner>/<repo>
+  GHCR_IMAGE: ${{ env.GHCR_IMAGE }}
+
 jobs:
 
   build:
@@ -27,19 +36,11 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Log in to GitHub Docker Registry
-        # if: github.event_name != 'pull_request'
-        uses: docker/login-action@v3
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Extract metadata for publishing image
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/${{ github.repository }}
+          images: ${{ env.GHCR_IMAGE }}
 
       - name: Build and export to Docker local cache
         uses: docker/build-push-action@v6
@@ -51,19 +52,24 @@ jobs:
       - name: Test cli works in cached runtime image
         run: docker run --rm tag_for_testing uvx pycowsay 'hello ubuntu-devcontainer!'
 
-      # image names must be all lower case, meta does this for us to make tags
-      # but can't get the image name back out
-      - name: Generate image repo name
-        run: echo REGISTRY_IMAGE=ghcr.io/$(tr '[:upper:]' '[:lower:]' <<< "${{ github.repository }}") >> $GITHUB_ENV
+      - name: Log in to GitHub Docker Registry
+        # if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build and push by digest
         id: build
         # if: github.ref_type == 'tag'
         uses: docker/build-push-action@v6
         with:
           labels: ${{ steps.meta.outputs.labels }}
-          tags: ${{ env.REGISTRY_IMAGE }}
-          outputs: type=image,push-by-digest=true,name-canonical=true,push=true
+          annotations: ${{ steps.meta.outputs.annotations }}
+          outputs: type=image,name=${{ env.GHCR_IMAGE }},push-by-digest=true,name-canonical=true,push=true,oci-mediatypes=true
+          cache-from: type=gha,scope=${{ github.repository }}-${{ github.ref_name }}-${{ matrix.platform }}
+          cache-to: type=gha,scope=${{ github.repository }}-${{ github.ref_name }}-${{ matrix.platform }}
 
       - name: Export digest
         run: |
@@ -77,7 +83,6 @@ jobs:
           name: digests-linux-${{ matrix.arch }}
           path: ${{ runner.temp }}/digests/*
           if-no-files-found: error
-          retention-days: 1
 
   merge:
     runs-on: ubuntu-latest
@@ -93,39 +98,34 @@ jobs:
           pattern: digests-*
           merge-multiple: true
 
-      - name: Log in to GitHub Docker Registry
-        uses: docker/login-action@v3
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
       - name: Create tags for publishing image
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/${{ github.repository }}
+          images: ${{ env.GHCR_IMAGE }}
           tags: |
             type=ref,event=pr
 
 #            type=ref,event=tag
 #            type=raw,value=latest
 #            type=raw,value=noble
 
-      # image names must be all lower case, meta does this for us to make tags
-      # but can't get the image name back out
-      - name: Generate image repo name
-        run: echo REGISTRY_IMAGE=ghcr.io/$(tr '[:upper:]' '[:lower:]' <<< "${{ github.repository }}") >> $GITHUB_ENV
+      - name: Log in to GitHub Docker Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Create manifest list and push
         working-directory: ${{ runner.temp }}/digests
         run: |
           docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
-            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
+            $(printf '${{ env.GHCR_IMAGE }}@sha256:%s ' *)
 
       - name: Inspect image
         run: |
-          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}
+          docker buildx imagetools inspect ${{ env.GHCR_IMAGE }}:${{ steps.meta.outputs.version }}