oras push fails when multiple tags are provided

[qweeah]

What happened in your environment?

oras push localhost:5000/test:a,b image
Error: invalid reference: invalid tag

What did you expect to happen?

Should successfully pushed the image.

oras-test push localhost:5000/test:a,b image
Uploading e3b0c44298fc image
Uploaded  e3b0c44298fc image
Pushed [registry] localhost:5000/test:a
Tagged b
Digest: sha256:eaa3bcd4220bdaa91717c3fe84aff9e99f30489d7cee47afac84b85da8767c55

How can we reproduce it?

Run below command:

oras push localhost:5000/test:a,b image

What is the version of your ORAS CLI?

Version: 1.0.0-rc.1
Go version: go1.19.5
Git commit: a98931b
Git tree state: clean

What is your OS environment?

ubuntu 20.04

Are you willing to submit PRs to fix it?

• Yes, I am willing to fix it.