CI: Create a multiplatform docker image using docker buildx features #100

	name: Wattsi CI
	on:
	pull_request:
	branches: ['main']
	push:
	branches: ['main']

	env:
	REGISTRY: ghcr.io
	IMAGE_NAME: ${{ github.repository }}

	jobs:
	build:
	name: Build
	runs-on: ubuntu-latest
	permissions:
	contents: read
	packages: write
	steps:
	- name: Checkout
	uses: actions/checkout@v4
	with:
	fetch-depth: 0
	- name: Setup QEMU
	uses: docker/setup-qemu-action@v3
	with:
	platforms: linux/amd64,linux/arm64
	- name: Setup Docker Buildx
	uses: docker/setup-buildx-action@v3
	- name: Create version file
	run: \|
	git rev-list --count HEAD > src/version.inc
	- name: Build
	uses: docker/build-push-action@v5
	with:
	context: .
	load: true
	tags: ${{ env.IMAGE_NAME }}:test
	- name: Test
	# This minimal test also saves the version for us to use as a tag.
	run: \|
	WATTSI_VERSION=$(docker run "$IMAGE_NAME:test" --version \| cut -d' ' -f2)
	echo "WATTSI_VERSION=$WATTSI_VERSION" >> $GITHUB_ENV
	- name: Login
	if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
	uses: docker/login-action@v3
	with:
	registry: ${{ env.REGISTRY }}
	username: ${{ github.actor }}
	password: ${{ secrets.GITHUB_TOKEN }}
	- name: Build and push
	if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
	uses: docker/build-push-action@v5
	with:
	context: .
	push: true
	platforms: linux/amd64,linux/arm64
	tags: \|
	${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.WATTSI_VERSION }}
	${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest

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