Gitlab CI setup to build the discourse docker image on a docker-based gitlab-runner

.gitlab-ci.yml

services:
  - name: postgres:12-alpine
    alias: bootstrap-postgres
  - name: redis:6
    alias: bootstrap-redis

variables:
  POSTGRES_DB: bootstrap
  POSTGRES_USER: bootstrap
  POSTGRES_PASSWORD: ''
  POSTGRES_HOST_AUTH_METHOD: trust
  FF_NETWORK_PER_BUILD: "true"

build:
  image: docker:latest
  stage: build
  script:
    - config=web_only
    - version=stable
    - apk add --update coreutils bash git grep jq
    - git clone --depth=1 https://github.com/discourse/discourse_docker /var/discourse
    - sed -i "s/__DISCOURSE_VERSION__/$version/g" "$config.yml"
    - cp "$config.yml" /var/discourse/containers
    - cd /var/discourse
    - mkdir /var/lib/docker
    - container="$(cat /proc/self/cgroup | grep -o 'docker/.*' | grep -Po '[^/]+$' | uniq)"
    - echo "$container"
    - network="$(docker inspect $container | jq -r '.[0].NetworkSettings.Networks | keys[]')"
    - echo "$network"
    - ./launcher bootstrap "$config" --docker-args "--net=$network"
    - build_image_name="local_discourse/$config:latest"
    - deploy_image_name="SOME_REGISTRY/discourse:$version-$config"
    - docker image tag "$build_image_name" "$deploy_image_name"
    - docker image rm "$build_image_name"
    - docker image push "$deploy_image_name"

web_only.yml

# IMPORTANT: SET A SECRET PASSWORD in Postgres for the Discourse User
# TODO: change SOME_SECRET in this template

templates:
  - "templates/web.template.yml"
  - "templates/web.ratelimited.template.yml"
## Uncomment these two lines if you wish to add Lets Encrypt (https)
  #- "templates/web.ssl.template.yml"
  #- "templates/web.letsencrypt.ssl.template.yml"

## which TCP/IP ports should this container expose?
## If you want Discourse to share a port with another webserver like Apache or nginx,
## see https://meta.discourse.org/t/17247 for details
expose:
  - "80:80"   # http
  - "443:443" # https

params:
  ## Which Git revision should this container use? (default: tests-passed)
  version: __DISCOURSE_VERSION__

env:
  LANG: en_US.UTF-8
  # DISCOURSE_DEFAULT_LOCALE: en

  ## How many concurrent web requests are supported? Depends on memory and CPU cores.
  ## will be set automatically by bootstrap based on detected CPUs, or you can override
  # UNICORN_WORKERS: 3

  ## TODO: The domain name this Discourse instance will respond to
  DISCOURSE_HOSTNAME: 'localhost'

  ## Uncomment if you want the container to be started with the same
  ## hostname (-h option) as specified above (default "$hostname-$config")
  #DOCKER_USE_HOSTNAME: true

  ## TODO: List of comma delimited emails that will be made admin and developer
  ## on initial signup example 'user1@example.com,user2@example.com'
  DISCOURSE_DEVELOPER_EMAILS: 'me@example.com,you@example.com'

  ## TODO: The SMTP mail server used to validate new accounts and send notifications
  # SMTP ADDRESS, username, and password are required
  # WARNING the char '#' in SMTP password can cause problems!
  DISCOURSE_SMTP_ADDRESS: localhost
  #DISCOURSE_SMTP_PORT: 587
  DISCOURSE_SMTP_USER_NAME: user@example.com
  DISCOURSE_SMTP_PASSWORD: pa$$word
  #DISCOURSE_SMTP_ENABLE_START_TLS: true           # (optional, default true)

  ## If you added the Lets Encrypt template, uncomment below to get a free SSL certificate
  #LETSENCRYPT_ACCOUNT_EMAIL: me@example.com
  
  ## TODO: configure connectivity to the databases
  DISCOURSE_DB_SOCKET: ''
  DISCOURSE_DB_USERNAME: bootstrap
  DISCOURSE_DB_PASSWORD: ''
  DISCOURSE_DB_HOST: bootstrap-postgres
  DISCOURSE_DB_NAME: bootstrap
  DISCOURSE_REDIS_HOST: bootstrap-redis

  ## The http or https CDN address for this Discourse instance (configured to pull)
  ## see https://meta.discourse.org/t/14857 for details
  #DISCOURSE_CDN_URL: https://discourse-cdn.example.com

volumes:

## Plugins go here
## see https://meta.discourse.org/t/19157 for details
#hooks:
#  after_code:
#    - exec:
#        cd: $home/plugins
#        cmd:
#          - git clone https://github.com/discourse/docker_manager.git

## Remember, this is YAML syntax - you can only have one block with a name
run:
  - exec: echo "Beginning of custom commands"

  ## If you want to configure password login for root, uncomment and change:
  ## Use only one of the following lines:
  #- exec: /usr/sbin/usermod -p 'PASSWORD_HASH' root
  #- exec: /usr/sbin/usermod -p "$(mkpasswd -m sha-256 'RAW_PASSWORD')" root

  ## If you want to authorized additional users, uncomment and change:
  #- exec: ssh-import-id username
  #- exec: ssh-import-id anotherusername

  - exec: echo "End of custom commands"
  - exec: awk -F\# '{print $1;}' ~/.ssh/authorized_keys | awk 'BEGIN { print "Authorized SSH keys for this container:"; } NF>=2 {print $NF;}'