pyproject.toml target-version support is undocumented

[adamchainz]

Is this related to a problem? Please describe.

Issue #3124 / PR #3219 added support for parsing --target-version from [project.requires-python] in pyproject.toml. But I can’t find any mention of this in the docs for --target-version or elsewhere.

Describe the solution you'd like

A paragraph describing the support and limitations, with an example.

Describe alternatives you've considered

Keeping this a secret feature 👎

Additional context

n/a

[hugovk]

Good idea, see also:

• https://ichard26.github.io/blog/2023/01/black-23.1.0/#better-default-for---target-version-if-pep-621-python-requires-is-available
• https://github.com/psf/black/blob/main/CHANGES.md#configuration-4