Attempt to separate builds into stages and skip base image build if i…

…t exists.

.github/workflows/spack_cpu_build.yaml

@@ -13,13 +13,11 @@ env:
 on: [pull_request]
 
 jobs:
-  base_image_build:
+  checkout_code:
+    name: Checkout code
     runs-on: ubuntu-22.04
     permissions:
-      packages: write
       contents: read
-
-    name: Build Custom Base Image
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -28,6 +26,46 @@ jobs:
           # Also need to change build script to use spack from base image
           submodules: true
 
+  check_for_image:
+    name: Check for image
+    runs-on: docker.io/kfox1111/misc:skopeo
+    permissions:
+      packages: read
+    steps:
+      # https://docs.github.com/en/actions/publishing-packages/publishing-docker-images
+      # This isn't necessary for skopeo, but spack will need this to push later...
+      - name: Log in to the Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ env.USERNAME }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Use skopeo to check for image for convenience
+      - name: Check for existing base images
+        run: |
+          set -e
+          CONTAINER_TAG=${{ env.BASE_VERSION }}
+          OCI_URL="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.BASE_VERSION }}"
+          echo Checking for CONTAINER_TAG $CONTAINER_TAG
+          mkdir -p /etc/gitlab-runner/certs
+          skopeo inspect \
+              docker://$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
+
+  base_image_build:
+    if: ${{ env.IMAGE_EXISTS == false }}
+    runs-on: ubuntu-22.04
+    permissions:
+      packages: write
+      contents: read
+
+    name: Build Custom Base Image
+
+    steps:
       # Need to build custom base image with gfortran
       - name: Create Dockerfile heredoc
         run: |
@@ -47,14 +85,6 @@ jobs:
               && rm -rf /var/lib/apt/lists/*
           EOF
 
-      # https://docs.github.com/en/actions/publishing-packages/publishing-docker-images
-      - name: Log in to the Container registry
-        uses: docker/login-action@v3
-        with:
-          registry: ${{ env.REGISTRY }}
-          username: ${{ env.USERNAME }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@v5