Use buildkit for GitLab-CI builds

image: docker:stable

variables:

  DOCKER_HOST: "tcp://docker:2375/"

  DOCKER_DRIVER: "overlay2"

  DOCKER_TLS_CERTDIR: ""

  DOCKER_BUILDKIT: "1"

services:

- docker:dind

before_script:

- docker info

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

.build: &build

  stage: build

  image: docker.kodo.org.uk/ci-images/buildkit/buildctl:latest

  tags: [buildkit]

  script:

  - TARGET=${CI_JOB_NAME##*:}

  - BUILD_TAG=${CI_REGISTRY_IMAGE}/${TARGET}/build:${CI_PIPELINE_ID}

  - docker build .

    --pull=true

    --tag=${BUILD_TAG}

    --target=${TARGET}

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

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

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

  - docker push ${BUILD_TAG}

  - buildctl build

    --frontend=dockerfile.v0

    --local context=.

    --local dockerfile=.

    --opt target=${TARGET}

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

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

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

    --output type=image,name=${BUILD_TAG},push=true

.changes: &only-changes

  only: &change-files