oras manifest fetch fails on oci image layout target

[qweeah]

What happened in your environment?

I have an image tagged test stored in oci-root folder, I am able to pull it but unable to use oras manifest fetch to get the manifest content.

What did you expect to happen?

oras manifest fetch should show the manifest content of oci-root\:test

How can we reproduce it?

$ echo image > image

$ oras push oci-root/:test image --oci-layout

$ oras repo tags oci-root --oci-layout
test

$ oras pull oci-root/:test --oci-layout
Downloading 0d566894635a image
Downloaded  0d566894635a image
Pulled [oci-layout] oci-root/:test
Digest: sha256:b311ca6afe69cec37e3cf3d6a56369be78de91bb0523dbdf4c40a23a65d7a0d1       

$ oras manifest fetch oci-root/:test --oci-layout
Error: not found

What is the version of your ORAS CLI?

I build it from the main branch of ORAS (last commit: 735ce35)

What is your OS environment?

20.04

Are you willing to submit PRs to fix it?

• Yes, I am willing to fix it.