support skipping image building with [image skip] in commit message

Author: daler

.github/workflows/build-images.yml

@@ -27,7 +27,7 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Detect existing images on quay.io
+      - name: Decide whether we should build
         id: detect-existing
         run: |
 
@@ -37,17 +37,25 @@ jobs:
           # Display the current environment variables used throughout building
           # -- useful for debugging
           env_var_inventory
+          set -x
+
+          if [[ "$(git log -1 --pretty=%B | head -n 1)" == *"[image skip]"* ]]; then
+
+            if tag_exists $BASE_BUSYBOX_IMAGE_NAME latest \
+            && tag_exists $BASE_DEBIAN_IMAGE_NAME latest \
+            && tag_exists $BUILD_ENV_IMAGE_NAME latest \
+            && tag_exists $BOT_IMAGE_NAME latest \
+            && tag_exists $ISSUE_RESPONDER_IMAGE_NAME latest \
+            && tag_exists $CREATE_ENV_IMAGE_NAME latest; then
+              echo "DO_BUILD=false" >> $GITHUB_OUTPUT
+            else
+              echo "Although '[image skip]' was used in the commit message, no images exist on quay.io to use. So images will be built."
+              echo "DO_BUILD=true" >> $GITHUB_OUTPUT
+          fi
 
-          if tag_exists $BASE_BUSYBOX_IMAGE_NAME $BASE_TAG \
-          && tag_exists $BASE_DEBIAN_IMAGE_NAME $BASE_TAG \
-          && tag_exists $BUILD_ENV_IMAGE_NAME $BIOCONDA_IMAGE_TAG \
-          && tag_exists $BOT_IMAGE_NAME $BIOCONDA_IMAGE_TAG \
-          && tag_exists $ISSUE_RESPONDER_IMAGE_NAME $BIOCONDA_IMAGE_TAG \
-          && tag_exists $CREATE_ENV_IMAGE_NAME $BIOCONDA_IMAGE_TAG;
-          then
-            echo "DO_BUILD=false" >> $GITHUB_OUTPUT
           else
             echo "DO_BUILD=true" >> $GITHUB_OUTPUT
+
           fi
 
   build-images:
@@ -156,18 +164,21 @@ jobs:
     # Download tarballs created in the previous job
     - name: Download images as artifacts
       uses: actions/download-artifact@v4
+      if: ${{ needs.detect-existing.outputs.DO_BUILD == 'true' }}
       with:
         name: image-artifacts
         path: image-artifacts
 
     # Load those tarballs as images into podman.
     - name: Load image artifacts into podman
+      if: ${{ needs.detect-existing.outputs.DO_BUILD == 'true' }}
       run: |
           for image in image-artifacts/*.tar; do
             podman load -i $image
           done
 
     - name: Build & push manifests to local docker registry
+      if: ${{ needs.detect-existing.outputs.DO_BUILD == 'true' }}
       run: |
 
         # Source env vars and functions to be used throughout building.
@@ -221,10 +232,23 @@ jobs:
         # registry running on localhost (which simulates eventually using
         # manifests from quay.io)
         source images/image_config.sh
-        export DEFAULT_BASE_IMAGE="localhost:5000/${BASE_BUSYBOX_IMAGE_NAME}:${BASE_TAG}"
-        export DEFAULT_EXTENDED_BASE_IMAGE="localhost:5000/${BASE_DEBIAN_IMAGE_NAME}:${BASE_TAG}"
-        export BUILD_ENV_IMAGE="localhost:5000/${BUILD_ENV_IMAGE_NAME}:${BIOCONDA_IMAGE_TAG}"
-        export CREATE_ENV_IMAGE="localhost:5000/${CREATE_ENV_IMAGE_NAME}:${BIOCONDA_IMAGE_TAG}"
+
+        # If we built images in this CI run, then use them -- otherwise use the
+        # latest on quay.io
+        if [ "${{ needs.detect-existing.outputs.DO_BUILD }}" == "true" ]; then
+          registry="localhost:5000"
+          base_tag="${BASE_TAG}"
+          bioconda_image_tag="${BIOCONDA_IMAGE_TAG}"
+        else
+          registry="quay.io/bioconda/"
+          base_tag="latest"
+          bioconda_image_tag="latest"
+        fi
+
+        export DEFAULT_BASE_IMAGE="${registry}/${BASE_BUSYBOX_IMAGE_NAME}:${base_tag}"
+        export DEFAULT_EXTENDED_BASE_IMAGE="${registry}/${BASE_DEBIAN_IMAGE_NAME}:${base_tag}"
+        export BUILD_ENV_IMAGE="${registry}/${BUILD_ENV_IMAGE_NAME}:${bioconda_image_tag}"
+        export CREATE_ENV_IMAGE="${registry}/${CREATE_ENV_IMAGE_NAME}:${bioconda_image_tag}"
 
         # Now that everything is set up, run the actual tests -- but only those
         # related to docker. The other tests are run in a different GitHub