ci: use matrix build for multi-arch build

[jpbernius]

This simplifies your @actions config by replacing duplication with a matrix configuration.

[tisonkun]

I don't know if this syntax works but we can merge it to main and see.

[tisonkun]

Broken - The workflow is not valid. .github/workflows/docker.yml (Line: 49, Col: 7): Unrecognized named-value: 'matrix'. Located at position 1 within expression: matrix.arch

[jpbernius]

Hi @tisonkun, sorry about that.

I had another look and from what I see there would be one option to make this work.
We would need to add an intermediate job which helps us put the matrix value into the output names (Source).
Something like this could work:

  build-and-push-hawkeye:
    ...
    steps:
     ...
+     - name: Matrix Output Converter
+       id: output
+       run: |
+         echo "digest-${{ matrix.arch }}=${{ steps.build.outputs.digest }}" >> $GITHUB_OUTPUT
    outputs:
-     digest-${{ matrix.arch }}: ${{ steps.build.outputs.digest }}
+     digest-amd64: ${{ steps.output.outputs.digest-amd64 }}
+     digest-arm64: ${{ steps.output.outputs.digest-arm64 }}

But, TBH, I am not sure if this is still an improvement. Let me know what you think.

[tisonkun]

I guess this doesn't work because the job finished later will override both outputs or the opposite.

IIRC I ever try to avoid duplicate and read a lot of GitHub Actions' docs but end up with the current solution. But it can be more than one year ago :D