bake: allow annotations to be set on the command line

[jsternberg]

Annotations were not merged correctly. The overrides in ArrValue would be merged, but the section of code setting them from the command line did not include annotations in the list of available attributes so the command line option was completely discarded.

Fixes #2989.

[crazy-max]

Should we do the same for labels?

[crazy-max]

https://github.com/docker/buildx/blob/master/docs/reference/buildx_bake.md#-override-target-configurations-from-command-line---set should be updated

[jsternberg]

For what it's worth, I don't think labels has the same issue. It uses Value from the overrides:

buildx/bake/bake.go

Lines 891 to 898 in 52f503e

	case "labels":
	if len(keys) != 2 {
	return errors.Errorf("invalid format for labels, expecting labels.<name>=<value>")
	}
	if t.Labels == nil {
	t.Labels = map[string]*string{}
	}
	t.Labels[keys[1]] = &value

Compare to annotations:

buildx/bake/bake.go

Lines 973 to 974 in 52f503e

	case "annotations":
	t.Annotations = append(t.Annotations, o.ArrValue...)

So this might already work for labels? It looks like it's documented in there to work.

[jsternberg]

Just to clarify, this switch is a list of "use ArrValue to fill in the overrides" and the default is to use Value if you're not in the list.

[crazy-max]

Ah yes indeed, thanks