Use the local value of TMPDIR when copying images over SSH.

[gordonmessmer]

Does this PR introduce a user-facing change?

Changed the behavior of podman-image-scp, such that the local TMPDIR will be used for 
temporary files on the destination.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: gordonmessmer
Once this PR has been reviewed and has the lgtm label, please assign n1hility for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[gordonmessmer]

This PR doesn't fix #21239 , but it does make it easier for users to do something about the failure.

[rhatdan]

You need to add a test or add [NO NEW TESTS NEEDED], you need to document this change in the man pages. (I am not sure this is the correct thing to do. Would it be better to add a --remote-tmpdir option to make the user specify this.

[edsantiago]

Sadly, this is probably not the best approach: $TMPDIR on my laptop/desktop != that on my remote server != etc.

@containers/podman-maintainers this is one of my stupid questions but why are we doing this in two stages (copy, load) instead of one (ssh host podman load -, with suitable input redirection)?

[Luap99]

@containers/podman-maintainers this is one of my stupid questions but why are we doing this in two stages (copy, load) instead of one (ssh host podman load -, with suitable input redirection)?

I have no idea but I agree that is how it should be done.

In any case I tend to agree that using the local TMPDIR on a remote server seems to be problematic

[gordonmessmer]

I've opened PR #21420 to replace this one.