.gitlab-ci.yml

image: docker:19.03.1

services:
  - docker:19.03.1-dind

before_script:
  - docker info
  - echo -n $CI_JOB_TOKEN | docker login -u $CI_REGISTRY_USER --password-stdin $CI_REGISTRY

stages:
  - build
  - tests
  - push

build-docker-image:
  stage: build
  tags:
    - dind
  script:
    - docker pull $CI_REGISTRY_IMAGE:latest || true
    - docker build --pull --cache-from $CI_REGISTRY_IMAGE:latest --tag $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA --build-arg FOLDERS_TO_REMOVE="spec node_modules vendor/assets lib/assets tmp/cache" --build-arg BUNDLE_WITHOUT="development:test" --build-arg RAILS_ENV="production" .
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

test-docker-image:
  stage: tests
  image: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
  before_script:
    - ''
  tags:
    - shell
  script:
    - ''

# Here, the goal is to tag the "master" branch as "latest"
Push latest:
  variables:
    # We are just playing with Docker here.
    # We do not need GitLab to clone the source code.
    GIT_STRATEGY: none
  stage: push
  tags:
    - dind
  only:
    # Only "master" should be tagged "latest"
    - master
  script:
    # Because we have no guarantee that this job will be picked up by the same runner
    # that built the image in the previous step, we pull it again locally
    - docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
    # Then we tag it "latest"
    - docker tag $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA $CI_REGISTRY_IMAGE:latest
    # And we push it.
    - docker push $CI_REGISTRY_IMAGE:latest

# Finally, the goal here is to Docker tag any Git tag
# GitLab will start a new pipeline every time a Git tag is created, which is pretty awesome
Push tag:
  variables:
    # Again, we do not need the source code here. Just playing with Docker.
    GIT_STRATEGY: none
  stage: push
  tags:
    - dind
  only:
    # We want this job to be run on tags only.
    - tags
  script:
    - docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
    - docker tag $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME