Add GH action to build multi-arch Docker image

[romainreignier]

This Github Action workflow allows to build the image for amd64, armv7 and arm64 platforms.

This should fix #83

The images are not built on Docker Hub itself but on Github runners following this blog post.
You have to add Github secrets DOCKER_HUB_USERNAME and DOCKER_HUB_ACCESS_TOKEN for this repo and disable Automated Build on Docker Hub if enabled.

You might want to precise the branch on which the action is triggered (not the case here to allow me to test on my branch) at the beginning:

on:
  push:
    branches:
      - master

You can see that this action works on my fork: https://github.com/romainreignier/docker-pure-ftpd/actions
And images are pushed to my Docker Hub account: https://hub.docker.com/r/rreignier/pure-ftpd/tags?page=1&ordering=last_updated

Produced images have been tested on amd64 and arch64.

[stilliard]

Hi @romainreignier ,
This looks great, thanks for the contribution!

This is good timing too as I noticed emails from Docker saying automated builds may be going away soon though I've reached out to them to see if this open source project will be included in that.

I'll need to do a little reading around how this works to make sure I keep the existing docker tags updated but I should have some time over the weekend to do this, thanks!

[romainreignier]

Hi @stilliard

Great!

Yes, the documentation about multi-arch Docker is a bit sparse and building directly on Docker Hub involves some hook tricks.
I have found the Github workflow simpler with the actions provided by Docker.

[mhenrixon]

@stilliard @romainreignier any plans on getting such an image to the docker repository?