Livepush does not support COPY --from<url> syntax

[pipex]

Expected Behavior

During balena push <local-ip> if the Dockerfile has an instruction

COPY --from=<image-url> <src> <tgt>

The build should succeed and the engine should automatically pull the referenced image

Actual Behavior

The push command fails with

DockerfileParseError: Could not find stage with name: ghcr.io/astral-sh/uv:latest
    at Dockerfile.stageNameToIndex (/snapshot/balena-cli/node_modules/livepush/build/dockerfile.js:193:19)
    at Dockerfile.parse (/snapshot/balena-cli/node_modules/livepush/build/dockerfile.js:134:70)
    at new Dockerfile (/snapshot/balena-cli/node_modules/livepush/build/dockerfile.js:17:14)
    at LivepushManager.preprocessDockerfile (/snapshot/balena-cli/build/utils/device/live.js:152:16)
    at /snapshot/balena-cli/build/utils/device/deploy.js:193:35

This can be confirmed to be a livepush issue because balena push <local-ip> --nolive works

Steps to Reproduce the Problem

Create a dockerfile that uses the given COPY instruction, e.g.

FROM alpine:latest
COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv
RUN apk add --no-cache curl
CMD ["curl", "https://www.google.com"]

From the folder where the file is located run

balena push <local-ip>

Where <local-ip> is the address of a balena device in local mode

Specifications

• balena CLI version: 20.2.1