Improvements to GCP testing workflow

.github/actions/cit-run-with-retry/action.yml

@@ -55,6 +55,10 @@ inputs:
     description: "Optional path to a JSONL file the script appends quota-failure records to. Used by the workflow to upload an artifact and aggregate an end-of-run quota summary."
     required: false
     default: ""
+  image_ref:
+    description: "Container image to run. Defaults to the prebuilt upstream image; pass a custom tag (e.g. `cit-custom:run-<run_id>`) when the workflow built CIT from source via the build-cit job."
+    required: false
+    default: "gcr.io/compute-image-tools/cloud-image-tests:latest"
 
 runs:
   using: composite
@@ -76,4 +80,5 @@ runs:
         RETRY_DELAY_SECONDS: ${{ inputs.retry_delay_seconds }}
         CREDS_PATH: ${{ inputs.creds_path }}
         QUOTA_LOG_FILE: ${{ inputs.quota_log_file }}
+        CIT_IMAGE: ${{ inputs.image_ref }}
       run: "${{ github.action_path }}/../../scripts/cit-run-with-retry.sh"

.github/scripts/cit-run-with-retry.sh

@@ -22,6 +22,9 @@
 #   CREDS_PATH           host path to GCP creds JSON
 #   QUOTA_LOG_FILE       optional JSONL file to append quota-failure records to.
 #                        Used by the workflow to aggregate a quota summary.
+#   CIT_IMAGE            container image to run. Defaults to the upstream
+#                        prebuilt; set to a locally-loaded tag when the
+#                        workflow's build-cit job is active.
 
 set -uo pipefail
 
@@ -148,7 +151,7 @@ for i in "${!attempts[@]}"; do
   "${RUNTIME}" run \
     -v "${CREDS_PATH}:/creds/auth.json" \
     -e GOOGLE_APPLICATION_CREDENTIALS=/creds/auth.json \
-    gcr.io/compute-image-tools/cloud-image-tests:latest \
+    "${CIT_IMAGE:-gcr.io/compute-image-tools/cloud-image-tests:latest}" \
     -project "${PROJECT}" \
     ${PARALLEL_COUNT:+-parallel_count ${PARALLEL_COUNT}} \
     ${PARALLEL_STAGGER:+-parallel_stagger ${PARALLEL_STAGGER}} \