Add direct unpack support for overlay and aufs

Signed-off-by: Lantao Liu <lantaol@google.com>

diff/apply/apply_other.go

@@ -0,0 +1,34 @@
+// +build !linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package apply
+
+import (
+	"context"
+	"io"
+
+	"github.com/containerd/containerd/archive"
+	"github.com/containerd/containerd/mount"
+)
+
+func apply(ctx context.Context, mounts []mount.Mount, r io.Reader) error {
+	return mount.WithTempMount(ctx, mounts, func(root string) error {
+		_, err := archive.Apply(ctx, root, r)
+		return err
+	})
+}