legacy docker config is not supported

[qweeah]

What happened in your environment?

Suppose we have below configuration in the registry config file:

{
  ...
  "auths": {
    "https://my.registry.io/": {
      "auth": "************",
      "email": ""
    }
  }
  ...
}

ORAS commands won't pick up the stored auth credentials when interacting with registry my.registry.io

What did you expect to happen?

If this legacy format is not deprecated, ORAS should use the credentials in the docker config with legacy format.

How can we reproduce it?

1. Change the stored credentials into legacy format: Found an entry of your registry config file, add prefix https:// to the registry key name to the entry.
2. Use ORAS commands against the modified registry, if authentication is required, the command will end with 401.

What is the version of your ORAS CLI?

v1.1.0

What is your OS environment?

Ubuntu 20.04

Are you willing to submit PRs to fix it?

• Yes, I am willing to fix it.

[qweeah]

Fixed by #1154