My gitlab ci file for build-test-release-deploy ing django docker image.

.gitlab-ci.yml

image: docker:stable

before_script:
  - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
  - apk update && apk add -y openssh-client
  - eval $(ssh-agent -s)
  - echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add - > /dev/null
  - mkdir -p ~/.ssh
  - chmod 700 ~/.ssh
  - ssh-keyscan $DEVELOP_SERVER >> ~/.ssh/known_hosts
  - ssh-keyscan $PRODUCTION_SERVER >> ~/.ssh/known_hosts
  - chmod 644 ~/.ssh/known_hosts

stages:
  - build
  - test
  - release
  - deploy

build_develop:
  stage: build
  only:
    - develop
  script:
    - echo "building docker image..."
    - docker build --cache-from $CI_REGISTRY_IMAGE:latest -t $CI_REGISTRY_IMAGE -f Dockerfile .
    - echo "build done"

build_master:
  stage: build
  only:
    - master
  script:
    - echo "building docker image..."
    - docker build --cache-from $CI_REGISTRY_IMAGE:stable -t $CI_REGISTRY_IMAGE -f Dockerfile .
    - echo "build done"

test:
  stage: test
  before_script:
    - docker run -d -p 8000:8000 -e "DEBUG=1" --name $CI_PROJECT_NAME-app-container $CI_REGISTRY_IMAGE
  script:
    - echo "running tests..."
    - docker exec -t $CI_PROJECT_NAME-app-container coverage run manage.py test
    - docker exec -t $CI_PROJECT_NAME-app-container coverage report -m
    - echo "test done"
  after_script:
    - docker stop $CI_PROJECT_NAME-app-container
    - docker rm $CI_PROJECT_NAME-app-container
  coverage: '/TOTAL.*\s+([\d\.]+%)$/'

release_develop:
  stage: release
  only:
    - develop
  script:
    - echo "releasing docker latest image..."
    - docker tag $CI_REGISTRY_IMAGE $CI_REGISTRY_IMAGE:$CI_COMMIT_SHORT_SHA
    - docker tag $CI_REGISTRY_IMAGE $CI_REGISTRY_IMAGE:latest
    - docker push $CI_REGISTRY_IMAGE:latest
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHORT_SHA
    - echo "release done"

release_master:
  stage: release
  only:
    - master
    - merge_requests
  script:
    - echo "releasing docker stable image..."
    - docker tag $CI_REGISTRY_IMAGE $CI_REGISTRY_IMAGE:stable
    - docker push $CI_REGISTRY_IMAGE:stable
    - echo "release done"

deploy_develop:
  stage: deploy
  only:
    - develop
  script:
    - echo "deploying to develop server..."
    - ssh $CI_PROJECT_NAME@$DEVELOP_SERVER "docker pull $CI_REGISTRY_IMAGE:latest && docker-compose up -d"

deploy_master:
  stage: deploy
  only:
    - master
    - merge_requests
  script:
    - echo "deploying to develop server..."
    - ssh $CI_PROJECT_NAME@$PRODUCTION_SERVER "docker pull $CI_REGISTRY_IMAGE:stable && docker-compose up -d"

Used docker socket binding scheme for gitlab runner. $SSH_PRIVATE_KEY, $DEVELOP_SERVER and $PRODUCTION_SERVER are repository-specific environment variables.