Describe the bug
First, I compressed a directory which has many files. And then I decompressed it. But the decompressed one is not a directory. It was a file. So, I cannot get in to the directory to search a specific file that I want.

To Reproduce

1. $ zstd -r --ultra DIRECTORY -o DIRECTORY.zst
2. $ zstd -d DIRECTORY.zst
3. decompressed one is not a directory!

Expected behavior
I just wanted to get my file. but '$ cd DIRECTORY' doesn't work.

Desktop (please complete the following information):

• OS: ubuntu 18.04
• Version: zstd CLI 64-bits v1.4.5