FROM busybox
USER ${user:-some_user}
ARG user
USER $user
RUN echo $CONT_IMG_VER

ARG  CODE_VERSION=latest
FROM base:${CODE_VERSION}
CMD  /code/run-app

FROM extras:${CODE_VERSION}
CMD  /code/run-extras

----------------------------------------------------

[
	["instruction", [
		["keyword", "FROM"],
		" busybox"
	]],
	["instruction", [
		["keyword", "USER"],
		["variable", "${user:-some_user}"]
	]],
	["instruction", [
		["keyword", "ARG"],
		" user"
	]],
	["instruction", [
		["keyword", "USER"],
		["variable", "$user"]
	]],
	["instruction", [
		["keyword", "RUN"],
		" echo ",
		["variable", "$CONT_IMG_VER"]
	]],

	["instruction", [
		["keyword", "ARG"],
		"  CODE_VERSION=latest"
	]],
	["instruction", [
		["keyword", "FROM"],
		" base:",
		["variable", "${CODE_VERSION}"]
	]],
	["instruction", [
		["keyword", "CMD"],
		"  /code/run-app"
	]],

	["instruction", [
		["keyword", "FROM"],
		" extras:",
		["variable", "${CODE_VERSION}"]
	]],
	["instruction", [
		["keyword", "CMD"],
		"  /code/run-extras"
	]]
]