Expose Pip's --use-feature.

[jsirois]

Folks may want to use these features. It could be the case that a feature breaks Pex, but that could be ameliorated with a warning in the option docs. In particular, its probably the case that most Pex (and Pip) users are unaware of the 3.5 year old --use-feature fast-deps range request hack for grabbing wheel metadata that uv is now using to much fanfare.

[jsirois]

This may not be needed. You can pass this option in a -r requirements.txt file already.

[jsirois]

A quick test of --use-feature fast-deps for torch shows its actually slightly slower.

That leads -> pypa/pip#8670 -> pypa/pip#11481 -> pypa/pip#12208 (unmerged)

So I'll close this since the option is already available using Pex (since Pex supports -r / --requirements) and the impetus to expose 1st class is not yet viable.