Add build cache support to CI builds

# Copyright (c) 2020 Dominik Sekotill <dom.sekotill@kodo.org.uk>

#

# This Source Code Form is subject to the terms of the Mozilla Public

# License, v. 2.0. If a copy of the MPL was not distributed with this

# file, You can obtain one at http://mozilla.org/MPL/2.0/.

#

values() {

	CACHE_IMG=${CI_REGISTRY_IMAGE}/${TARGET}/cache

	RW_CACHE1=${CACHE_IMG}:latest

	RW_CACHE2=${CACHE_IMG}:${CI_COMMIT_REF_NAME}

	RW_CACHE3=${CACHE_IMG}:${CI_COMMIT_SHA}

	RO_CACHE1=${CACHE_IMG}:${CI_COMMIT_BEFORE_SHA}

}

cache_arg() {

	values

	arg="--cache-from=${RW_CACHE1},${RW_CACHE2},${RW_CACHE3},${RO_CACHE1}"

	sed -n 's/FROM \([^ ]*:[^ ]*\).*/\1/p' Dockerfile |

		while read image; do arg+=",$image"; done

	echo "$arg"

}

push_cache() (

	values

	for tag in ${RW_CACHE1} ${RW_CACHE2} ${RW_CACHE3}; do

		docker tag $1 ${tag}

		docker push ${tag}

	done

)

before_script:

- docker info

- docker login -u gitlab-ci-token -p "$CI_JOB_TOKEN" "$CI_REGISTRY"

- . .gitlab-ci.d/funcs.sh

.build: &build

  stage: build

    --pull=true

    --tag=${BUILD_TAG}

    --target=${TARGET}

    --build-arg BUILDKIT_INLINE_CACHE=1

    $(cache_arg)

    ${NGINX_VERSION:+--build-arg=nginx_version=$NGINX_VERSION}

    ${PHP_VERSION:+--build-arg=php_version=$PHP_VERSION}

    ${WORDPRESS_VERSION:+--build-arg=wp_version=$WORDPRESS_VERSION}

  - docker push ${BUILD_TAG}

  - push_cache ${BUILD_TAG}

.changes: &only-changes

  only: &change-files