squash-docker-save

#!/bin/bash

set -e
set -o pipefail

function list_tars {
	ROOT=$1
	TAG=${2:-latest}
	BASE=$(sed -e 's/.*{\(".*"\)}.*/\1/g' "${ROOT}/repositories" | sed 's/"//g' | awk -v RS=',' -F: '/^'${TAG}'/ {print $2}')
	CUR=$BASE
	while [[ -f "${ROOT}/${CUR}/json" ]]; do
		PARENT=$(sed -e 's/.*{\(".*"\)}.*/\1/g' ${ROOT}/${CUR}/json | sed 's/"//g' | awk -v RS=',' -F: '/^parent/ {print $2}')
		if [[ "${PARENT}" != "" ]]; then
			echo ${PARENT}
		fi
		CUR=${PARENT}
	done | tac
	echo ${BASE}
}

[[ "$1" == "" ]] && {
	echo "please provide docker image to squash!"
	exit -1
}

[[ "$2" == "" ]] && {
	echo "please provide out folder!"
	exit -1
}

OUT=$2
ROOT="${OUT}/.out"
TAG=":${3:-latest}"
mkdir -p "${ROOT}"

docker pull $1$TAG
docker save $1$TAG | tar -C "${ROOT}" -xf-

for p in $(list_tars ${ROOT} $3); do
	f="${ROOT}/${p}/layer.tar"
	if [[ -f "${f}" ]]; then
		tar --numeric-owner -C "${OUT}" -xf "${f}"
	fi
done

rm -fr "${ROOT}"