.travis.yml

# The following environment variables need to be defined in the Travis UI:
#   DOCKERHUB_USER ....... for deploying docker images to DockerHub
#   DOCKERHUB_PASSWORD ... (secret) for deploying docker images to DockerHub
#   GITHUB_TOKEN ......... (secret) for creating a GitHub Release
os: linux
dist: xenial  # Ubuntu: 16.04 (xenial), 18.04 (bionic)
language: shell
services: docker
git:
  depth: 1

jobs:
  include:
    # Build instructions for one stage (= docker build), one Debian version.
    - &build-env
      stage: build-env
      # This build is expensive O(hours).
      # Only run on dedicated deployment branch.
      if: branch = deploy
      arch: arm64
      env: debian_version=stretch
      before_install: &env_setup
        - export GITHUB_REPO="${TRAVIS_REPO_SLUG/*\//}"
        - export GITHUB_USER="${TRAVIS_REPO_SLUG/\/*/}"
      # We use before_script instead of script because we want to error out at
      # the first sign of trouble.
      before_script:
        - stage="$(echo ${TRAVIS_BUILD_STAGE_NAME} | tr '[A-Z]' '[a-z]')"
        # For some reason executing a function with 'set -e; f' hangs Travis
        # on error in the function, whereas 'bash -ec f' errors the build as
        # expected.
        - bash -ec "source ./build-functions.sh; build ${stage}"
        - docker login -u="$DOCKERHUB_USER" -p="$DOCKERHUB_PASSWORD"
        - bash -ec "source ./build-functions.sh; push ${stage}"
    # Do the same (in parallel) for other Debian versions.
    - <<: *build-env
      env: debian_version=buster
    - <<: *build-env
      env: debian_version=bullseye

    # This stanza repeats for every build stage. It's rather obscure and ugly,
    # but Travis' expressibility for job dependencies is quite limited. This is
    # the most concise way I have found to express an approximation of the
    # actual dependencies.
    - &server-deb
      <<: *build-env
      stage: server-deb
    - <<: *server-deb
      env: debian_version=buster
    - <<: *server-deb
      env: debian_version=bullseye

    - &server
      <<: *build-env
      stage: server
    - <<: *server
      env: debian_version=buster
    - <<: *server
      env: debian_version=bullseye

    - &desktop-deb
      <<: *build-env
      stage: desktop-deb
    - <<: *desktop-deb
      env: debian_version=buster
    - <<: *desktop-deb
      env: debian_version=bullseye

    - stage: Create GitHub Release
      if: tag IS NOT blank
      arch: amd64  # This can run on a regular x86 host.
      before_install: *env_setup
      install: |
        # Install GitHub API script.
        bash -ec "source ./build-functions.sh; install_github_api"
      script: |
        # Create a new draft release.
        bash -ec "source ./build-functions.sh; \
                  create_github_release $TRAVIS_TAG stretch buster bullseye"