Using set overides rather than merges with array settings in docker-bake.hcl

[ncrmro]

Contributing guidelines

• I've read the contributing guidelines and wholeheartedly agree

I've found a bug, and:

• The documentation does not mention anything about my problem
• There are no open or closed issues that are related to my problem

Description

It appears target sets are not merged with existing array and instead overide settings in the bake file.

Specifically cache-from's set in the action's set are not merged with cache froms in the the bake file

Expected behaviour

Given a docker-bake.hcl

target "foobar" {
  context = "."
  dockerfile = "Dockerfile"
  cache-release-from = [
    "type=registry,ref=ghcr.io/exampeorg/foobar:cache-release-development-staging"
  ]
}

And an action that sets cache-from, cache-to

      - name: Build and cache foobartarget
        uses: docker/bake-action@v6
        with:
          source: .
          targets: foobar
          files: docker-bake.hcl
          set: |
           foobar.cache-from=type=registry,ref=gghcr.io/exampeorg/foobar:cache-pr-development-PR-0000
            foobar.cache-to=type=registry,ref=ghcr.io/exampeorg/foobar:cache-pr-development-PR-0000,mode=max

Will result in a bake definition

  {
    "group": {
      "default": {
        "targets": [
          "foobar"
        ]
      }
    },
    "target": {
      "foobar": {
        "attest": [
          {
            "type": "provenance"
          }
        ],
        "context": ".",
        "dockerfile": "Dockerfile",
        "cache-from": [
          {
            "ref": "ghcr.io/exampeorg/foobar:cache-release-development-staging",
            "type": "registry"
          },
          {
            "ref": "ghcr.io/exampeorg/foobar:cache-pr-development-PR-0000",
            "type": "registry"
          }
        ],
        "cache-to": [
          {
            "mode": "max",
            "ref": "ghcr.io/exampeorg/foobar:cache-pr-development-PR-0000",
            "type": "registry"
          }
        ],
        "target": "foobar"
      }
    }
  }

Actual behaviour

I would expect this to merge and result in.

  {
    "group": {
      "default": {
        "targets": [
          "foobar"
        ]
      }
    },
    "target": {
      "foobar": {
        "attest": [
          {
            "type": "provenance"
          }
        ],
        "context": ".",
        "dockerfile": "Dockerfile",
        "cache-from": [
          {
            "ref": "ghcr.io/exampeorg/foobar:cache-pr-development-PR-0000",
            "type": "registry"
          }
        ],
        "cache-to": [
          {
            "mode": "max",
            "ref": "ghcr.io/exampeorg/foobar:cache-pr-development-PR-0000",
            "type": "registry"
          }
        ],
        "target": "foobar"
      }
    }
  }

### Repository URL

_No response_

### Workflow run URL

_No response_

### YAML workflow

```yaml
See expected behavor.

Workflow logs

No response

BuildKit logs

Additional info

No response

[crazy-max]

Thanks for reporting, this is a bug in Buildx 0.20.0 that has been already addressed in docker/buildx#2944. Buildx 0.20.1 will go out today with the fix.