hostedtoolcache directory and environment variables for it #369

	name: Docker Image Build

	on:
	push:
	branches: [ master ]
	paths:
	- '*/Dockerfile'
	pull_request:
	branches: [ master ]
	paths:
	- '*/Dockerfile'

	jobs:
	files:
	runs-on: ubuntu-latest

	outputs:
	matrix: ${{ steps.dockerfile.outputs.matrix }}

	steps:
	- name: Checkout repository
	uses: actions/checkout@v2
	with:
	fetch-depth: 0

	- name: Get changed files
	id: files
	uses: jitterbit/get-changed-files@v1
	with:
	format: json

	- name: Extract Dockerfile files
	id: dockerfile
	run: \|
	FILES=$( echo '${{ steps.files.outputs.added_modified }}' \| jq -c 'map(select(. \| endswith("Dockerfile")))' )
	echo "matrix=$FILES" >> "$GITHUB_OUTPUT"

	build:
	runs-on: ubuntu-latest
	needs: files

	strategy:
	fail-fast: false
	matrix:
	dockerfile: ${{ fromJSON(needs.files.outputs.matrix) }}

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

	- name: Build Docker image ${{ matrix.dockerfile }}
	run: \|
	cd "$(dirname ${{ matrix.dockerfile }})"
	docker build . --file Dockerfile

Provide feedback