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The RUN --mount=type=bind syntax allows mounting files or directories of images into a Docker build step. One advantage over the already supported COPY --from=<tag> syntax is that the number of layers can be reduced when copying multiple files from the same image:

# Produces 3 layers
COPY --from=node:21.7.0-alpine /etc/group /etc
COPY --from=node:21.7.0-alpine /etc/passwd /etc
COPY --from=node:21.7.0-alpine /usr/local/bin/node /usr/local/bin

# vs.

# Produces 1 layer
RUN \
  --mount=type=bind,from=node:21.7.0-alpine,source=/,target=/mnt \
  cp -a /mnt/etc/group /etc/group && \
  cp -a /mnt/etc/passwd /etc/passwd && \
  cp -a /mnt/usr/local/bin/node /usr/local/bin/node

Recently, I discovered that Renovate updates Docker image tags in COPY --from=<tag> instructions, but not in RUN --mount=type=bind,from=<tag> instructions.

I would like Renovate to support both cases.