Add `--all-variants` option to show debug builds in `uv python list`

[albanD]

Summary

Truncated result is

$ uv python list --only-downloads
cpython-3.14.0rc3-linux-x86_64-gnu                       <download available>
cpython-3.14.0rc3+freethreaded-linux-x86_64-gnu          <download available>
cpython-3.14.0rc3+freethreaded+debug-linux-x86_64-gnu    <download available>
cpython-3.13.7-linux-x86_64-gnu                          <download available>
cpython-3.13.7+freethreaded-linux-x86_64-gnu             <download available>
cpython-3.13.7+freethreaded+debug-linux-x86_64-gnu       <download available>
... more cpython versions below

But these versions can actually be installed

$ uv python install 3.13+debug
cpython-3.13.7+debug-linux-x86_64-gnu (download) ...

Platform

Linux 6.15.3-100.fc41.x86_64 x86_64 GNU/Linux (Fedora)

Version

uv 0.8.19

Python version

3.12.3

[zanieb]

uv/crates/uv/src/commands/python/list.rs

Lines 113 to 114 in 8f3583a

	// TODO(zanieb): Add a way to show debug downloads, we just hide them for now
	.filter(|download| download.key().variant() != &uv_python::PythonVariant::Debug);

We hide these intentionally. We need an --all-variants option or something.

[zanieb]

This needs a little design work, but should be pretty easy.

[albanD]

That sounds good!
I would also suggest hiding the PythonVariant::FreethreadedDebug when this option is not passed in.

[zanieb]

Definitely, that was an oversight.

[zanieb]

We should also emit debug builds if it's included in the request, e.g., uv python list 3.13+debug