bake: move merge logic to gohcl package and add tests

Signed-off-by: CrazyMax <[email protected]>

Author: crazy-max

bake/bake.go

@@ -16,6 +16,7 @@ import (
 
 	composecli "github.com/compose-spec/compose-go/v2/cli"
 	"github.com/docker/buildx/bake/hclparser"
+	"github.com/docker/buildx/bake/hclparser/gohcl"
 	"github.com/docker/buildx/build"
 	controllerapi "github.com/docker/buildx/controller/pb"
 	"github.com/docker/buildx/util/buildflags"
@@ -343,7 +344,7 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, _ *hclpars
 
 	var pm hclparser.ParseMeta
 	if len(hclFiles) > 0 {
-		res, err := hclparser.Parse(hclparser.MergeFiles(hclFiles), hclparser.Opt{
+		res, err := hclparser.Parse(gohcl.MergeFiles(hclFiles), hclparser.Opt{
 			LookupVar:     os.LookupEnv,
 			Vars:          defaults,
 			ValidateLabel: validateTargetName,

bake/hclparser/merged.go bake/hclparser/gohcl/merged.go

@@ -1,9 +1,7 @@
 // Copyright (c) HashiCorp, Inc.
 // SPDX-License-Identifier: MPL-2.0
 
-// Forked from https://github.com/hashicorp/hcl/blob/4679383728fe331fc8a6b46036a27b8f818d9bc0/merged.go
-
-package hclparser
+package gohcl
 
 import (
 	"fmt"