gitlab pipeline with external docker dind

.gitlab-ci.yaml

stages:
  - build
  - test
  - deploy
    
variables:
  # disable Docker TLS validation
  DOCKER_TLS_CERTDIR: ""
  # here the dind hostname is resolved as the Kubernetes dind service by the kube dns
  DOCKER_HOST: "tcp://dind:2375"

docker-build:
  image: docker:stable
  stage: build
  script:
    - docker build -t hello .
    - docker tag hello:latest my-registry/hello:{CI_COMMIT_SHORT_SHA}
    - docker push my-registry/hello:{CI_COMMIT_SHORT_SHA}