Python: Honour --strip-extras flag of pip-compile

[NicolasT]

The --strip-extras flag of pip-compile is useful to generate
contstraints files (instead of the more traditional requirements files)
from some constraints.in file.

Constraints files can't have extras markers on the packages (this
wouldn't make much sense indeed), hence they need to be stripped. Since
pip-tools 6.2.0 this is supported by using the --strip-extras flag.

This commit adds this as a 'recognized' flag: if it's found in an
existing foo.txt file, it will be passed to pip-compile when some
foo.in file is updated.

See: #3974 (comment)
See: #3974 (comment)
See: jazzband/pip-tools#1300 (comment)

[NicolasT]

(Note: I have no clue whether this is the right approach to add tests, and how to actually write proper tests in the given framework. Not a Ruby'ist either. So this is very much hit-and-miss)

[jurre]

I think this makes sense, letting CI run to make sure there aren't any unexpected side-effects, but thanks for contributing!

[NicolasT]

Not sure how this change can cause a Bundler test to fail 🤔

[jurre]

Not sure how this change can cause a Bundler test to fail 🤔

That's not related, it's a known flaky test unfortunately

[NicolasT]

Thanks for merging!

Are there any docs on how one can know whether/when this change landed in the Github-hosted Dependabot service?

[NicolasT]

Looks like it's in prod, and it's achieving the desired result: I now get 'correct' (without extras) Dependabot PRs for my constraints.txt. Sweet!

[jurre]

Are there any docs on how one can know whether/when this change landed in the Github-hosted Dependabot service?

No docs on this currently, but typically once a PR is included in a release (you should get a mention in the release notes), we'll roll that out in production the same or next day.

Thanks again for the contribution!