Support use of top level domains

[pxc1984]

Signed-off-by: Igor igor.mamaev1@gmail.com

closes #27424

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Does this PR introduce a user-facing change?

Podman now supports top-level domains

[mtrmac]

⚠️ NAK (compare #27424 (comment) ).

No, we are not going to diverge any more from 10-year-established string semantics . It’s bad enough that we have short name lookups when half of ecosystem always expands to docker.io[/library], and that leads to serious problems (see the warning in https://docs.redhat.com/en/documentation/openshift_container_platform/4.9/html/images/image-configuration )

Adding even more optionality to the semantics, having the same string be a short name on some systems and not be a short name on others, for a feature that should never be used for deployments in any other site, is not worth doing.

I don’t dispute that the risks and problems of this don’t matter in some specific home networks. Nevertheless:

• No-one should ever write and package software with instructions “to deploy this software, edit registries.conf in a way that potentially breaks short names of other deployments; that’s not reasonable when users almost always want to run software from several sources side by side [that equivalently applies to “configure short names to point at our software”].
• No-one should ever recommend “design your home lab so that the registry has a single-component host name and refer to images that way, it works fine” — users will find themselves painted in a corner with no way to proceed but to redesign entirely.

If you must, use the same registries.conf to define short-name aliases from top-level/repo/image to top-level:443/repo/image or similar.

(I intentionally did not add any other comments.)