Add dockerBuildxPlatforms

[barryoneill]

Continuing on #2590, this allegedly will trigger buildx during a CI build

[mzuehlke]

Did you tried if this locally would build a multi arch image ?
CI isn't a help here ...

[barryoneill]

Sorry, I phrased that badly. Adding dockerBuildxPlatforms should trigger Docker / publish to use buildx to generate the multi-arch manifests.

Unfortunately, I can't use Docker / publish locally, since I use podman as my container engine and it doesn't support the necessary push flags. Docker / publishLocal will use the regular build mechanisms, which is what I use locally, hence my comment about CI.

If I have time this week I'll try and find/setup a non-podman environment to test this.

[barryoneill]

Alright, I think I have made progress. For anyone else fighting with this on mac m1 - don't use podman. I switched to orbstack, and added the following to the 'Advanced Engine Config' in the orbstack settings:

{
  "features" : {
    "containerd-snapshotter" : true
  }
}

And I was able to use sbt Docker / publish up till it tried to publish to Docker hub (which of course I don't have permission to :))

I changed the supported architectures to what I could see in eclipse-temurin:21-alpine, i.e.

❯ docker manifest inspect eclipse-temurin:21-alpine | jq '.manifests[].platform'
{
  "architecture": "amd64",
  "os": "linux"
}
{
  "architecture": "arm64",
  "os": "linux",
  "variant": "v8"
}

@mzuehlke Should be good to go now.

[mzuehlke]

Thanks for investigating, makes sense 👍

[mzuehlke]

I reverted this PR, because publishing failed: https://github.com/scala-steward-org/scala-steward/actions/runs/11083098359/job/30797020608

It seems the whole publish docker procedure would need to be adapted su support using buildx like described here:
https://docs.docker.com/build/building/multi-platform/

[barryoneill]

To me it seems like this project would be better served by building the docker image manually, giving more direct control over the build process, rather than being limited by whatever sbt-docker is doing with buildx under the hood.

Might also be easier to just wait till later in the year and build on arm64 when github makes it available open source projects later in the year, but that would mean duplicate builds, rather than one buildx invocation.

@mzuehlke I really appreciate the help with these PRs, sorry it didn't work out. Can you please reopen #2590 in case someone else wants to get involved!

[mzuehlke]

I reopened the ticket