gist for https://attonblog.blogspot.com/2020/06/github-actions-dockerfile-build.html

build-and-push.yml

# Original: https://github.com/atton/dockerfiles/blob/1566be5489c34ba743dd5735f6584d3ef213cdb5/.github/workflows/build-and-push.yml

name: Build and Push Docker Images

on: push

jobs:
  build-and-push:
    runs-on: ubuntu-latest
    steps:
    - name: Clone repository
      run: git clone https://github.com/atton/dockerfiles
    - name: Build and Push Docker Images
      run: sh dockerfiles/build.sh ${{ secrets.DOCKER_PASSWORD }}      

build.sh

# Original: https://github.com/atton/dockerfiles/blob/1566be5489c34ba743dd5735f6584d3ef213cdb5/build.sh

#!/bin/sh
cd `dirname $0`

git show --name-only

if [ -n "$1" ]; then docker login -u atton -p $1; fi
for name in `ls`; do
    if [ ! -d $name ]; then continue; fi
    if [ ! -f $name/Dockerfile ]; then continue; fi

    tag="atton/$name"
    docker build --compress --pull -t $tag $name

    git diff-tree --no-commit-id --name-only -r master | grep "$name/" >/dev/null 2>&1
    if [ $? -eq 0 ]; then docker push $tag; fi
done
if [ -n "$1" ]; then docker logout; fi