oci-image-tool: Cleanup partially-unpacked directories on failures

Signed-off-by: Lei Jitang <leijitang@huawei.com>

Author: coolljt0725

image/manifest.go

@@ -87,7 +87,22 @@ func (m *manifest) validate(w walker) error {
 	return nil
 }
 
-func (m *manifest) unpack(w walker, dest string) error {
+func (m *manifest) unpack(w walker, dest string) (retErr error) {
+	// error out if the dest directory is not empty
+	if s, err := ioutil.ReadDir(dest); err != nil && err != os.IsNotExist(err) || len(s) > 0 {
+		if err != nil {
+			return fmt.Errorf("failed to open %s: %v", dest, err)
+		}
+		return fmt.Errorf("%s is not empty", dest)
+	}
+	defer func() {
+		// if we encounter error during unpacking
+		// clean up partially-unpacked destination
+		if retErr != nil {
+			os.RemoveAll(dest)
+		}
+	}()
+
 	for _, d := range m.Layers {
 		if d.MediaType != string(schema.MediaTypeImageConfig) {
 			continue