finish env var docs #14

	name: Build backend image

	on:
	push:

	env:
	REGISTRY: ghcr.io
	DOCKERFILE: ./docker/api/Dockerfile
	IMAGE_NAME: ${{ github.repository }}
	IMAGE_KIND: backend

	jobs:
	backend-build:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2

	- name: Docker meta
	id: meta
	uses: docker/metadata-action@v3
	with:
	flavor: \|
	latest=auto
	suffix=-${{ env.IMAGE_KIND }},onlatest=false
	tags: \|
	type=sha
	type=edge,branch=main
	type=raw,value={{date 'YYYY-MM-DD-HH-mm'}},enable={{is_default_branch}}
	images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

	- name: Set up QEMU
	uses: docker/setup-qemu-action@v1

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

	- name: Login to DockerHub
	uses: docker/login-action@v1
	with:
	registry: ${{ env.REGISTRY }}
	username: ${{ github.actor }}
	password: ${{ secrets.GITHUB_TOKEN }}

	- name: Cache Docker layers
	uses: actions/cache@v2
	with:
	path: /tmp/.buildx-cache
	key: ${{ runner.os }}-buildx-${{ github.sha }}
	restore-keys: ${{ runner.os }}-buildx

	- name: Build and push
	id: docker_build
	uses: docker/build-push-action@v2
	with:
	context: .
	file: ${{ env.DOCKERFILE }}
	push: true
	tags: ${{ steps.meta.outputs.tags }}
	cache-from: type=local,src=/tmp/.buildx-cache
	cache-to: type=local,dest=/tmp/.buildx-cache-new

	# Temp fix
	# https://github.com/docker/build-push-action/issues/252
	# https://github.com/moby/buildkit/issues/1896
	- name: Move cache
	run: \|
	rm -rf /tmp/.buildx-cache
	mv /tmp/.buildx-cache-new /tmp/.buildx-cache

	- name: Image digest
	run: echo ${{ steps.docker_build.outputs.digest }}

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