add github action to generate docker image for builder #1

	name: Build and publish docker image

	on:
	push:
	# Publish `master` as Docker `latest` image.
	branches:
	- master
	- develop

	# Publish `v1.2.3` tags as releases.
	tags:
	- '*'
	env:
	IMAGE_NAME: openwrt-builder

	jobs:
	# Push image to GitHub Packages.
	# See also https://docs.docker.com/docker-hub/builds/
	push:
	runs-on: ubuntu-latest
	permissions:
	packages: write
	contents: read

	steps:
	- uses: actions/checkout@v3

	- name: Build image
	run: docker build . --file Dockerfile --tag $IMAGE_NAME --label "runnumber=${GITHUB_RUN_ID}"

	- name: Log in to registry
	# This is where you will update the PAT to GITHUB_TOKEN
	run: echo "${{ secrets.GITHUB_TOKEN }}" \| docker login ghcr.io -u $ --password-stdin

	- name: Push image
	run: \|
	IMAGE_ID=ghcr.io/${{ github.repository_owner }}/$IMAGE_NAME

	# Change all uppercase to lowercase
	IMAGE_ID=$(echo $IMAGE_ID \| tr '[A-Z]' '[a-z]')
	# Strip git ref prefix from version
	VERSION=$(echo "${{ github.ref }}" \| sed -e 's,./$.$,\1,')
	# Strip "v" prefix from tag name
	[[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION \| sed -e 's/^v//')
	# Use Docker `latest` tag convention
	[ "$VERSION" == "master" ] && VERSION=latest
	echo IMAGE_ID=$IMAGE_ID
	echo VERSION=$VERSION
	docker tag $IMAGE_NAME $IMAGE_ID:$VERSION
	docker push $IMAGE_ID:$VERSION

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