allow multi-node push and imagetools to use custom registry config

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/moby/buildkit/cmd/buildkitd/config/load.go

@@ -0,0 +1,36 @@
+package config
+
+import (
+	"io"
+	"os"
+
+	"github.com/pelletier/go-toml"
+	"github.com/pkg/errors"
+)
+
+// Load loads buildkitd config
+func Load(r io.Reader) (Config, error) {
+	var c Config
+	t, err := toml.LoadReader(r)
+	if err != nil {
+		return c, errors.Wrap(err, "failed to parse config")
+	}
+	err = t.Unmarshal(&c)
+	if err != nil {
+		return c, errors.Wrap(err, "failed to parse config")
+	}
+	return c, nil
+}
+
+// LoadFile loads buildkitd config file
+func LoadFile(fp string) (Config, error) {
+	f, err := os.Open(fp)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return Config{}, nil
+		}
+		return Config{}, errors.Wrapf(err, "failed to load config from %s", fp)
+	}
+	defer f.Close()
+	return Load(f)
+}