Use of FQIN in Dockerfile FROM instructions.

[gitouche-sur-osm]

Feature Description

This is a request for the use of Fully Qualified Image Names (FQIN) in Dockerfile FROM instructions.
eg. FROM alpine:3.17 -> FROM docker.io/library/alpine:3.17

The use of short names is ambiguous as the registry it pulls from might depend on docker (or alternative build system) configuration. This is better explained in containers-registries.conf man page.

Docker uses hardcoded configuration in order to search for short names on docker.io registry :

echo $(docker info | grep -oP "(?<=Registry: ).*")
https://index.docker.io/v1/

But this behaviour might be different if registry-mirrors is set in docker daemon.json.

This would also improve support for docker alternatives as well (e.g. buildah, where the docker.io HUB might not be the default registry), while staying 100% docker compatible.

Lines that would need patching :

gitea/Dockerfile

Line 2 in 797babb

FROM golang:1.20-alpine3.17 AS build-env

gitea/Dockerfile

Line 26 in 797babb

FROM alpine:3.17

gitea/Dockerfile.rootless

Line 2 in 797babb

FROM golang:1.20-alpine3.17 AS build-env

gitea/Dockerfile.rootless

Line 26 in 797babb

FROM alpine:3.17

Thank you for considering this request.

Screenshots

No response

[techknowlogick]

@gitouche-sur-osm thanks for the suggestion. I've just created a PR for this: #23955