build: docker images for latest release and main branch

[aucampia]

Summary of changes

This PR adds docker image building to the github actions workflow.

Two images are built:

• unstable: This is built from the current branch
• latest: This is built from the version of rdflib in
  docker/latest/requirements.txt, but as this will be updated by
  dependabot it will essentially always be the latest version.

The resulting image references are:

• ghcr.io/rdflib/rdflib:unstable
• ghcr.io/rdflib/rdflib:latest with an alias
  ghcr.io/rdflib/rdflib:${rdflib_version}, e.g.
  ghcr.io/rdflib/rdflib:6.2.0.

As dependabot is conifgured for both pyton and docker dependencies, any
change/update to dependencies will result in a new image being built.

To avoid spurious changes in image digests the existing image is used as
the cache source, so if the requirements.txt and Dockerfile for
ghcr.io/rdflib/rdflib:latest has not changed then a new image should
not be published for it even if the build runs.

I have tested this in my forked repo, but there may be some kinks to
still work out.

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[coveralls]

Coverage remained the same at 90.634% when pulling 3585c67 on aucampia:iwana-20220914T2257-docker_images into bcd05e9 on RDFLib:main.

[aucampia]

@nicholascar this could be somewhat simpler with poetry, at the very least the redudant requirements.txt files could be avoided somewhat, but otherwise it would be the same for the most part.

With poetry though you want to first export your dependencies to requirements.txt, something like:

poetry export --without-hashes --dev --format requirements.txt > requirements.txt

Then you would copy that requirements.txt file into the image.

If that file is not stable (i.e. if it fluctuates randomly for the same poetry.lock) then the caching will not work too well.

[aucampia]

Image can be used as follow:

$ echo '<ex:1> <ex:2> <ex:3> .' | docker run --rm -i ghcr.io/rdflib/rdflib:6.2.0 rdfpipe -i ntriples -o turtle -
@prefix ns1: <ex:> .

ns1:1 ns1:2 ns1:3 .

[aucampia]

Another way to use this:

$ docker run --rm -i ghcr.io/rdflib/rdflib:6.2.0 python -c 'import rdflib; g = rdflib.Graph(); g.add((rdflib.RDF.type, rdflib.RDF.type, rdflib.RDF.type, )); print(g.serialize())'
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

rdf:type a rdf:type .

[nicholascar]

@nicholascar this could be somewhat simpler with poetry, at the very least the redudant requirements.txt files could be avoided somewhat, but otherwise it would be the same for the most part.

With poetry though you want to first export your dependencies to requirements.txt, something like:

poetry export --without-hashes --dev --format requirements.txt > requirements.txt

Then you would copy that requirements.txt file into the image.

If that file is not stable (i.e. if it fluctuates randomly for the same poetry.lock) then the caching will not work too well.

I do think for a long-term stable repo, it's probably always worth having the requirements.txt file built so non-Poetry users can use it with PIP, however we could happily do the more efficient image building with Poetry as you say. That's where we're going across the board (on other projects).

Do you want to make this change?

[nicholascar]

@jamiefeiss can you please pick up the patterns used here for Prez?

[aucampia]

Do you want to make this change?

I will create a discussion to check with others what they think sometime, I like poetry a lot and use it extensively, but I also don't want to make things harder for others so best to just see the level of support there is.

[nicholascar]

@aucampia where do the images from this PR's creation scripts end up and how do people use them? I think that they might be private as I can't pull them from ghcr.io/rdflib/rdflib:latest etc. ("unauthorized").

I think we, or at least I!, need documentation on how to use the resultant images...

[aucampia]

@aucampia where do the images from this PR's creation scripts end up and how do people use them? I think that they might be private as I can't pull them from ghcr.io/rdflib/rdflib:latest etc. ("unauthorized").

The visibility needs to be changed here

But I don't think I can do it.

I think we, or at least I!, need documentation on how to use the resultant images...

I should add documentation and will when I can, hopefully this weekend or next week.