Publish builder images to same locations as buildpacks and stacks

[robdimsdale]

Describe the Enhancement

Currently we publish buildpacks and stacks to dockerhub and gcr, but we only publish builders to dockerhub. We should be consistent across all types of images, so we should publish builders to gcr.io as well as dockerhub.

Motivation

There have been a couple of requests over the past few days for publishing builders to gcr.io. (this issue and this slack thread).

[sophiewigmore]

Hey Rob. I agree our stuff should be consistent across the board. A long time ago, we had a plan to ideally stop publishing to GCR in the long run for cost purposes - https://github.com/paketo-buildpacks/rfcs/blob/main/text/0015-dockerhub-distribution.md?plain=1#L16-L17. I honestly don't know where this proposal ended up, its been ages but thought it seems relevant to think about this before we start pushing to GCR anywhere else

[sophiewigmore]

Also, this recent thread from @dmikusa has some GCR related concerns to consider - https://paketobuildpacks.slack.com/archives/C011S6EL49L/p1718741275733309

[dmikusa]

I know that we also had an RFC proposed to publish to other registries (like ECR), and it didn't get approved. The thought process against approving it was that it was beyond the scope of what the project should do. That if you, as a user, want them in a particular registry cause that's convenient for you, then you should mirror them to that registry. Mirror images is easy. That's a benefit of distributing things via images.

GCR is there for historical reasons. I don't remember an RFC that proposed removing it though. RFC0015 says that it could be deprecated but doesn't indicate a specific plan around how that will go or when that would happen. There's also the image retention policy RFC, which again mentions GCR being deprecated but doesn't call out anything specific about how/when it'll stop being used.

My guess is that historically these were never added to GCR because GCR was deprecated at the time these projects were created and we just assumed we'd stop using GCR in the near future. That never really happened though.

My $0.02...

• if you want to add the images to GCR to be consistent, that seems reasonable in the short term.
• I think we should have a specific RFC to go from deprecated to no longer used, that spells out the plan in detail. That's going to need to include announcements of the time frame for removal, etc...