Vendor in containers/buildah@v1.26.1

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/containers/buildah/internal/util/util.go

@@ -1,9 +1,18 @@
 package util
 
 import (
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/containers/buildah/define"
 	"github.com/containers/common/libimage"
 	"github.com/containers/image/v5/types"
 	"github.com/containers/storage"
+	"github.com/containers/storage/pkg/archive"
+	"github.com/containers/storage/pkg/chrootarchive"
+	"github.com/containers/storage/pkg/unshare"
+	"github.com/pkg/errors"
 )
 
 // LookupImage returns *Image to corresponding imagename or id
@@ -22,3 +31,51 @@ func LookupImage(ctx *types.SystemContext, store storage.Store, image string) (*
 	}
 	return localImage, nil
 }
+
+// ExportFromReader reads bytes from given reader and exports to external tar, directory or stdout.
+func ExportFromReader(input io.Reader, opts define.BuildOutputOption) error {
+	var err error
+	if !filepath.IsAbs(opts.Path) {
+		opts.Path, err = filepath.Abs(opts.Path)
+		if err != nil {
+			return err
+		}
+	}
+	if opts.IsDir {
+		// In order to keep this feature as close as possible to
+		// buildkit it was decided to preserve ownership when
+		// invoked as root since caller already has access to artifacts
+		// therefore we can preserve ownership as is, however for rootless users
+		// ownership has to be changed so exported artifacts can still
+		// be accessible by unpriviledged users.
+		// See: https://github.com/containers/buildah/pull/3823#discussion_r829376633
+		noLChown := false
+		if unshare.IsRootless() {
+			noLChown = true
+		}
+
+		err = os.MkdirAll(opts.Path, 0700)
+		if err != nil {
+			return errors.Wrapf(err, "failed while creating the destination path %q", opts.Path)
+		}
+
+		err = chrootarchive.Untar(input, opts.Path, &archive.TarOptions{NoLchown: noLChown})
+		if err != nil {
+			return errors.Wrapf(err, "failed while performing untar at %q", opts.Path)
+		}
+	} else {
+		outFile := os.Stdout
+		if !opts.IsStdout {
+			outFile, err = os.Create(opts.Path)
+			if err != nil {
+				return errors.Wrapf(err, "failed while creating destination tar at %q", opts.Path)
+			}
+			defer outFile.Close()
+		}
+		_, err = io.Copy(outFile, input)
+		if err != nil {
+			return errors.Wrapf(err, "failed while performing copy to %q", opts.Path)
+		}
+	}
+	return nil
+}