e2e/testdata/engine/Dockerfile - external/github.com/docker/cli - Git at Google

 ARG ENGINE_VERSION
 FROM docker:${ENGINE_VERSION}-dind

 # Trust the tlsregistry CA so dockerd connects without --insecure-registry.
 COPY registry/certs/ca.crt /usr/local/share/ca-certificates/tlsregistry-ca.crt
 RUN update-ca-certificates
	ARG ENGINE_VERSION
	FROM docker:${ENGINE_VERSION}-dind

	# Trust the tlsregistry CA so dockerd connects without --insecure-registry.
	COPY registry/certs/ca.crt /usr/local/share/ca-certificates/tlsregistry-ca.crt
	RUN update-ca-certificates