In Move function, output a warning when encountering an unexpected file.

convert.go

@@ -110,14 +110,15 @@ func Move(oldPath string, newPath string, out io.Writer) error {
 		if err != nil {
 			return err
 		}
-		if inf.IsDir() || fn == "SHARDING" || fn == "_README" {
-			// if we are a director or generated file just remove it
+		if inf.IsDir() || fn == SHARDING_FN || fn == README_FN {
+			// we are an empty directory or generated file so just remove it
 			err := os.Remove(oldPath)
 			if err != nil {
 				return err
 			}
 		} else {
-			// else move it
+			// else we found something unexpected, so to be safe just move it
+			log.Warningf("found unexpected file in datastore directory: \"%s\", moving anyway", fn)
 			newPath := filepath.Join(newDS.path, fn)
 			err := osrename.Rename(oldPath, newPath)
 			if err != nil {