ggcr: Parsing image name with both tag and digest loses tag info

[halamix2]

Describe the bug

When parsing image in repo.com/image:tag@sha256:f8ecdcd87d7d84b87e645074084dd7f57dd62c76e120bb21e5abde158755be56format it gets parsed as a Digest type, which returns digest from the ref.Identifier() function, and doesn't provide easy access to the tag information

I'm only using the name parsing, so I have no idea if this would have any negative impact on any other part of the library

To Reproduce

ref, _ := name.ParseReference(repo.com/image:tag@sha256:f8ecdcd87d7d84b87e645074084dd7f57dd62c76e120bb21e5abde158755be56")
fmt.Println(ref.Identifier()) // sha256:f8ecdcd87d7d84b87e645074084dd7f57dd62c76e120bb21e5abde158755be56
// fmt.Println(ref.Tag()) - doesn't exist

Expected behavior

I'd expect to have a ref.Tag() function in the Reference interface that can return image tag for both Tag and Digest structs, so that the tag name is always accessible

Additional context

• go-containerregistry v0.20.3

[vpnachev]

Looks like duplicate of #1768

[afdesk]

+1
Implementing this feature would be extremely useful!