Image versioning: Tag each docker build with a unique id, and push that to quay.io

[joerick]

Over at cibuildwheel we've been talking about how we might get some determinism in the build process (pypa/cibuildwheel#239), and the manylinux image is one of those things we'd like to lock down.

This PR introduces a docker tag, alongside latest, of the format YYYY-MM-dd-gitsha, for example 2020-01-18-dea2616. Each build is tagged, and the tag is pushed to quay.io.

I have tested this on my fork, with Travis building and uploading - see https://quay.io/repository/joerick/manylinux2010_x86_64?tab=tags for how these end up in quay.io.

Thanks!

Fixes #111

[joerick]

Any thoughts, @mayeut ?

[mayeut]

@joerick,
I'm going to merge this but there might be a need to define a retention strategy in order not to store too much over the years.
Given it's been less than 100GB/year and that quay.io states an unlimited storage in its FAQ, that seems ok for now but nevertheless, we should think about that.

Can you create similar PRs for manylinux1 & manylinux2014 branches ?
Thanks

[joerick]

Can you create similar PRs for manylinux1 & manylinux2014 branches ?

Done, see #470 and #471.

there might be a need to define a retention strategy in order not to store too much over the years.

Hm, yes. If quay.io could provide download stats, they could be used to delete images that weren't being used any more. I can't see that anywhere currently...

[joerick]

Thank you @mayeut !!