Repository: docker/compose
File: internal/registry/registry.go (Go)

Code before:
/*
   Copyright 2023 Docker Compose CLI authors

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package registry

const (
	// IndexHostname is the index hostname, used for authentication and image search.
	IndexHostname = "index.docker.io"
	// IndexServer is used for user auth and image search
	IndexServer = "https://index.docker.io/v1/"
	// IndexName is the name of the index
	IndexName = "docker.io"
	// LegacyRegistry is the legacy name of the inde
	LegacyRegistry = "registry-1.docker.io"
)

// GetAuthConfigKey special-cases using the full index address of the official
// index as the AuthConfig key, and uses the (host)name[:port] for private indexes.
func GetAuthConfigKey(indexName string) string {
	if indexName == IndexName || indexName == IndexHostname || indexName == LegacyRegistry {
		return IndexServer
	}
	return indexName
}


Review comment (suggestion):
This is actually the canonical, only correct  hostname of the registry 🫠 
https://github.com/moby/moby/blob/2670796a010406b6b35aaff1cdd02f4309e79060/daemon/pkg/registry/config.go#L40-L46

Code after:
/*
   Copyright 2023 Docker Compose CLI authors

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package registry

const (
	// DefaultNamespace is the default namespace
	DefaultNamespace = "docker.io"
	// DefaultRegistryHost is the hostname for the default (Docker Hub) registry
	// used for pushing and pulling images. This hostname is hard-coded to handle
	// the conversion from image references without registry name (e.g. "ubuntu",
	// or "ubuntu:latest"), as well as references using the "docker.io" domain
	// name, which is used as canonical reference for images on Docker Hub, but
	// does not match the domain-name of Docker Hub's registry.
	DefaultRegistryHost = "registry-1.docker.io"
	// IndexHostname is the index hostname, used for authentication and image search.
	IndexHostname = "index.docker.io"
	// IndexServer is used for user auth and image search
	IndexServer = "https://" + IndexHostname + "/v1/"
	// IndexName is the name of the index
	IndexName = "docker.io"
)

// GetAuthConfigKey special-cases using the full index address of the official
// index as the AuthConfig key, and uses the (host)name[:port] for private indexes.
func GetAuthConfigKey(indexName string) string {
	if indexName == IndexName || indexName == IndexHostname || indexName == DefaultRegistryHost {
		return IndexServer
	}
	return indexName
}