system tests: refactor registry code

[edsantiago]

The podman-login tests have accumulated much cruft over the
years, because that's the only place where we run a local
registry, and the process was crufty: we actually start/stopped
the registry as the first & last tests of the file. Meaning,
you couldn't do 'hack/bats 150:just-one-test' because that
would skip the registry start. And just now, a completely
unrelated test has had to be shoved into the login file.

This PR revamps the whole thing, by adding a new registry helper
module that can be used anywhere. And, once the registry is
started, it just stays running until the end of tests. (This
requires BATS 1.7 or greater).

Signed-off-by: Ed Santiago [email protected]

None

[vrothberg]

LGTM

I feel slight uncomfortable to have the registry run all the time though. Pushing images etc. has side effects on other tests.

But it's a tremendous improvement. Thank you!

[vrothberg]

#19092 includes this PR now ✔️

[rhatdan]

LGTM

[edsantiago]

I feel slight uncomfortable to have the registry run all the time though. Pushing images etc. has side effects on other tests.

I would like to understand this concern better. My thinking was that there is little cost to a registry running idle, it's just another background daemon process. (This is system tests. Serial. No tests will be pushing/pulling while other tests are running). Do registries run background maintenance or other expensive tasks? Can you tell me more about your concerns?

[vrothberg]

Do registries run background maintenance or other expensive tasks?

They maybe do some garbage collection and listen for incoming requests but I don´t expect this to cause noise.

Can you tell me more about your concerns?

My main concern is that tests share the same resource. So one test can influence another. For instance, pushing to this registry could break another test using the same image or searching on it.

It's a purely hypothetical scenario at the moment. I am not that worried about it now.

[edsantiago]

One clean CI run, no flakes. Re-pushing for confidence.

[edsantiago]

Four CI runs with no system-test flakes. I think this is good to go.

[vrothberg]

/lgtm

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