BUG: loading multiple images corrupts tags of existing ones

[h-vetinari]

[Now that I have access to the nightly ppa's (cf. #2250), here's some more things I found]

Sometimes it's necessary to transfer images in bulk (say, to an environment that has restricted internet access). Docker supports saving/loading multiple images, and nominally, podman does too. Loading multiple images saved by docker fails (xref #2822), while loading multiple images saved by podman go through but are either loading incorrectly or even corrupting tags that might have been correct before.

This is a much subtler issue and thus harder to detect.

Steps to reproduce:

$ sudo podman pull ubuntu:bionic
$ sudo podman pull ubuntu:cosmic

Then, things look as follows.

Saving and reloading corrupts the tags.

$ sudo podman save docker.io/library/ubuntu:bionic docker.io/library/ubuntu:cosmic > podman_test.tar
$ sudo podman load -i podman_test.tar

In particular, docker.io/library/ubuntu:cosmic gets wrongly tagged to the commit of docker.io/library/ubuntu:bionic, while the actual commit of docker.io/library/ubuntu:cosmic gets untagged.

Side note: in contrast to docker, there is no auto-completion for file-names after sudo podman load -i

[h-vetinari]

@haircommander
In view of your comment, and before containers/image#610 is fixed, this should IMO at least error loudly, rather than corrupt existing tags.

[baude]

@haircommander is this in your domain or do we need to get someone to pick it up?

[haircommander]

@baude it is generally out of my domain--it could be in my domain given some time (that I don't currently have) :)