Add check for existing base image to speedup pipelines.

.github/workflows/spack_cpu_build.yaml

@@ -32,8 +32,29 @@ jobs:
           # Also need to change build script to use spack from base image
           submodules: true
 
+      # No GHCR base image with skopeo, so this will do...
+      - name: "Set up skopeo"
+        uses: warjiang/[email protected]
+        with:
+          version: latest
+
+      # Use skopeo to check for image for convenience
+      - name: Check for existing base images
+        run: |
+          set -e
+          CONTAINER_TAG=${{ env.BASE_VERSION }}
+          OCI_URL="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.BASE_VERSION }}"
+          echo Checking for CONTAINER_TAG $CONTAINER_TAG
+          skopeo inspect \
+              docker://$OCI_URL \
+              --raw \
+              --creds "${{ env.USERNAME }}:${{ secrets.GITHUB_TOKEN }}" \
+            > /dev/null && echo "Image already exists. Please bump version." && exit 0
+          echo "IMAGE_EXISTS=false" >> $GITHUB_ENV
+
       # Need to build custom base image with gfortran
       - name: Create Dockerfile heredoc
+        if: ${{ env.IMAGE_EXISTS == 'false' }}
         run: |
           cat << EOF > Dockerfile
           FROM ubuntu:24.04
@@ -61,13 +82,15 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Extract metadata (tags, labels) for Docker
+        if: ${{ env.IMAGE_EXISTS == 'false' }}
         id: meta
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           labels: org.opencontainers.image.version=${{ env.BASE_VERSION }}
 
       - name: Build and push Docker base image
+        if: ${{ env.IMAGE_EXISTS == 'false' }}
         uses: docker/build-push-action@v5
         with:
           context: .