push-build.sh: push docker images from tarfiles

[ixdy]

Adds a --docker-registry flag to push-build.sh; if set, all images in _output/release-images will be pushed to the specified registry/project.

Depends on kubernetes/kubernetes#47939.
A part of addressing kubernetes/test-infra#1400.

cc @luxas @madhusudancs @roberthbailey

[david-mcmahon]

If the intention here is to replace release::docker::release(), why not do that all here as well too?

[ixdy]

This won't work for older releases (<k8s 1.8). I'm not sure I want to cherrypick my changes back.

At some point we could probably get rid of the existing release::docker::release().

[ixdy]

put another way: I don't want to change anything about anago until 1.7.0 is out. after that I may consider changing things.

[david-mcmahon]

Maybe check for /release-images/ somewhere here and dynamically use local images if they exist? Then this is backward compat and we can eventually remove release::docker::release() once we're beyond supporting <=1.7.

[david-mcmahon]

That's fine. I'd prefer to leave things in a state where they Just Work under any condition/version, but this can certainly co-exist. Please put loud TODOs here with context though so we eventually clean up.

[ixdy]

Good suggestions. I've made release::docker::release() call to release_from_tarfiles if the release-images directory exists, maintaining existing workflow otherwise.

[ixdy]

github does a terrible job displaying the diff, but I basically just indented here.

[ixdy]

the PR in k/k has merged. PTAL?

[luxas]

I don't have enough experience with these scripts to say anything, but I guess it's ok for me if it works ;)

[roberthbailey]

/lgtm

[ixdy]

gonna merge. this seems to work locally, but I'll watch CI/PR builds to make sure things are still working. fyi @krzyzacy @dchen1107