Add GH Action for pushing to Docker Hub on Release

[SanketDG]

Added the Github Action for automating pushing the pypa/bandersnatch
image to Docker Hub when a new release in published.

Closes #88

[codecov]

Codecov Report

Merging #482 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #482   +/-   ##
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  Coverage   81.59%   81.59%           
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  Files          10       10           
  Lines        1157     1157           
  Branches      168      168           
=======================================
  Hits          944      944           
  Misses        171      171           
  Partials       42       42           

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[cooperlees]

We already build on every commit to master. I feel we just need something to tag the build as the release.

1 way could be:

• See if commit has a Git tag and, if so, mirror it to docker hub tags?

[SanketDG]

I see.

Would using https://github.com/elgohr/Publish-Docker-Github-Action/blob/master/README.md#tag_names to tag the images work out?

[cooperlees]

Yup - Seems all we need is tag_names: true in .github/workflows/docker_upload.yml. Thanks for finding that!

[cooperlees]

There might be a race before the commit gets the release tag ...

• I wonder if it's re-ran when a tag is applied?

[SanketDG]

I wonder if it's re-ran when a tag is applied?

Interesting, let me test this out.

[SanketDG]

This is blocked for the meantime, my local Docker instance seems to be causing issues.

[SanketDG]

Pulled this from the graves! Apologies, I get what I deserve for distrohopping so frequently!
I have updated the changes to use tag_names for releases.

There might be a race before the commit gets the release tag ...

• I wonder if it's re-ran when a tag is applied?

So I tested this, and it seems like it only tags the image when an annotated tag (which is a tag + commit) is pushed, so it only creates an image with the tag name.

[cooperlees]

I say lets merge and see what happens :)