Function normalize_image_ref 

pub fn normalize_image_ref(image: &str) -> String

Canonicalize an OCI image reference.

All equivalent spellings of the same image produce an identical string, which is safe to use as a cache key or protocol field.

Normalization rules (applied in order)

1. index.docker.io is rewritten to docker.io (legacy alias).
2. A missing registry defaults to docker.io.
3. Single-component names on docker.io receive the library/ prefix (e.g. alpine → docker.io/library/alpine).
4. A missing tag defaults to :latest. When a digest (@sha256:…) is present it takes precedence and any tag is dropped.

Examples

use smolvm_protocol::normalize_image_ref;

assert_eq!(normalize_image_ref("alpine"),
           "docker.io/library/alpine:latest");
assert_eq!(normalize_image_ref("alpine:3.20"),
           "docker.io/library/alpine:3.20");
assert_eq!(normalize_image_ref("docker.io/alpine:3.20"),
           "docker.io/library/alpine:3.20");
assert_eq!(normalize_image_ref("docker.io/library/alpine:3.20"),
           "docker.io/library/alpine:3.20");
assert_eq!(normalize_image_ref("ghcr.io/owner/repo:v1"),
           "ghcr.io/owner/repo:v1");