docs: slightly easier README #240

	name: Docker

	on:
	push:
	branches: [main]
	tags:
	- "v*"
	pull_request:
	branches: [main]

	env:
	REGISTRY: ghcr.io
	IMAGE_NAME: ${{ github.repository}}
	PLATFORMS: linux/amd64,linux/arm64,linux/arm/v7,linux/arm/v6

	jobs:
	build:
	runs-on: ubuntu-latest
	permissions:
	contents: read
	packages: write

	steps:
	- name: Checkout repository
	uses: actions/checkout@v2

	- name: Set up QEMU
	uses: docker/setup-qemu-action@v1
	with:
	platforms: ${{ env.PLATFORMS }}

	- name: Set up Docker Buildx
	id: buildx
	uses: docker/setup-buildx-action@v1

	# Login against a Docker registry except on PR
	# https://github.com/docker/login-action
	- name: Log into registry ${{ env.REGISTRY }}
	uses: docker/login-action@v1
	with:
	registry: ${{ env.REGISTRY }}
	username: ${{ github.actor }}
	password: ${{ secrets.GITHUB_TOKEN }}

	# Extract metadata (tags, labels) for Docker
	# https://github.com/docker/metadata-action
	- name: Extract Docker metadata
	id: meta
	uses: docker/metadata-action@v3
	with:
	images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

	# Build and push Docker image with Buildx (don't push on PR)
	# https://github.com/docker/build-push-action
	- name: Build and push Docker image
	uses: docker/build-push-action@v2
	with:
	context: .
	platforms: ${{ env.PLATFORMS }}
	push: true
	tags: ${{ steps.meta.outputs.tags }}
	labels: ${{ steps.meta.outputs.labels }}

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