make previous build check fail gracefully

3_chunk.sh

@@ -27,7 +27,22 @@ PREV_MANIFEST=${PREV_MANIFEST:=./${PREV_NAME}.manifest.json}
 
 if [ -n "$PREV_REF" ]; then
     echo "PREV_REF is set, downloading manifest"
-    skopeo inspect docker://${PREV_REF} > $PREV_MANIFEST
+    for i in $(seq 1 5); do
+        skopeo inspect docker://${PREV_REF} > $PREV_MANIFEST && break
+        echo "Failed to download previous manifest, retrying in 3 seconds"
+        sleep 3
+    done
+
+    if [ ! -f "$PREV_MANIFEST" ]; then
+        echo "############################################"
+        echo "ERROR: Failed to download previous manifest"
+        if [ -n "$PREV_REF_FAIL" ]; then
+            echo "Failing build due to PREV_REF_FAIL being set."
+            exit 1
+        else
+            echo "Continuing build without previous manifest"
+        fi
+    fi
 fi
 
 # Try to use venv if it exists for

action.yml

@@ -14,6 +14,9 @@ inputs:
     description: |
       The previous image reference, if any. Used for versioning
       the current image and to avoid layer shifts (important; may be skipped).
+  prev-ref-fail:
+    description: |
+      If set, fail if the previous image reference is not found.
   max-layers:
     description: |
       The number of layers (chunks) the output image will have.
@@ -119,6 +122,7 @@ runs:
             -e VERSION="${{ inputs.version }}" \
             -e VERSION_FN="/workspace/version.txt" \
             -e OUT_REF="oci:$OUT_NAME" \
+            -e PREV_REF_FAIL="${{ inputs.prev-ref-fail }}" \
             -u 0:0 \
             ${{ inputs.rechunk }} \
             /sources/rechunk/3_chunk.sh