gh-142389: Add support for backtick colorisation in argparse help text

[hugovk]

#142390 added support for displaying text enclosed in backticks in colour for the help description and epilogue.

This PR adds it for individual help.

Also add backticks to python -m test --help:

Will add to other stdlib CLIs in a followup.

• Issue: Add support for colorizing code examples in argparse description/epilog #142389

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #32534304 | 📁 Comparing 634cfe6 against main (10f950c)

🔍 Preview build

3 files changed

±library/argparse.html
±whatsnew/3.15.html
±whatsnew/changelog.html

[savannahostrowski]

I think there's one edge case here that we haven't considered...and should before extending this to help text. Poking around on GitHub, flake8 uses double backticks to denote code in help text (I also found at least one instance of this in pytest as well but it's not as pervasive). So, right now, with these changes users would see something like this, where there are funky stray backticks and incorrect colouring:

I think if we apply the new regex, update the docs and add a test or two, that should have us covered.

Other than that, I think this looks good. My preference would be to land this feature and then land application of backticks in a separate PR though (i.e. we can leave libregrtest changes for another PR?)

[bedevere-app]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[hugovk]

Updated docs, docstring and added tests.

Removed the regrtest change, will be in a followup with other stdlib stuff.

I have made the requested changes; please review again.

[bedevere-app]

Thanks for making the requested changes!

@savannahostrowski: please review the changes made to this pull request.

[StanFromIreland]

We apply color before width is calculated, leading to some odd line breaks.

With NO_COLOR:

Whereas with color:

[hugovk]

We apply color before width is calculated, leading to some odd line breaks.

There's a separate issue for this somewhere, and maybe even a PR?

[hugovk]

My preference would be to land this feature and then land application of backticks in a separate PR though (i.e. we can leave libregrtest changes for another PR?)

Please see PR #149384.

[savannahostrowski]

Sweeeeet! Thank Hugo!

[alexprengere]

We apply color before width is calculated, leading to some odd line breaks.

There's a separate issue for this somewhere, and maybe even a PR?

I think this is the one #142035. The more colors applied, the more visible this will be 😉 .
IMO the clean solution would be to make some changes in textwrap.wrap, to handle graphemes and escape sequences (3.15 ships unicodedata.iter_graphemes). I would be happy to make those changes but I think this will be considered a new feature, thus should land in 3.16 now.