image: docker:stable

stages:
- build

services:
- docker:dind

variables:
  CONTAINER_IMAGE: $CI_REGISTRY/$CI_PROJECT_PATH

before_script:
  - docker info
  - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY

build_image:
  stage: build
  script: |
    COMMIT_DATE=`date +%Y%m%d%H%M`
    docker pull $CONTAINER_IMAGE:$CI_COMMIT_BRANCH || true
    docker build --cache-from $CONTAINER_IMAGE:$CI_COMMIT_BRANCH \
      --tag $CONTAINER_IMAGE:$CI_COMMIT_BRANCH-$COMMIT_DATE \
      --tag $CONTAINER_IMAGE:$CI_COMMIT_BRANCH \
      .
    docker push $CONTAINER_IMAGE:$CI_COMMIT_BRANCH-$COMMIT_DATE
    docker push $CONTAINER_IMAGE:$CI_COMMIT_BRANCH