The loose consensus is that "fetch" doesn't have much meaning and that a
boolean flag makes more sense from the command line.
1. Adds `--allow-python-downloads` (hidden, default) and
`--no-python-downloads` to the CLI to quickly enable or disable
downloads
2. Deprecates `--python-fetch` in favor of the options from (1)
3. Removes `python-fetch` in favor of a `python-downloads` setting
5. Adds a `never` variant to the enum, allowing even explicit installs
to be disabled via the configuration file
## Test plan
I tested this with various `pyproject.toml`-level settings and `uv venv
--preview --python 3.12.2` and `uv python install 3.12.2` with and
without the new CLI flags.
## Summary
After referring to https://github.com/astral-sh/uv/pull/5637 and doing
additional testing.
The default value in a stable state seems more reasonable to be
``only-system``. ``managed`` in preview.
```
cpython-3.11.9-windows-x86_64-none C:\Users\name\AppData\Local\Programs\Python\Python311\python.exe
cpython-3.10.14-windows-x86_64-none C:\Users\name\AppData\Roaming\uv\data\python\cpython-3.10.14-windows-x86_64-none\install\python.exe
cpython-3.10.11-windows-x86_64-none C:\Users\name\AppData\Local\Programs\Python\Python310\python.exe
cpython-3.9.19-windows-x86_64-none C:\Users\name\AppData\Roaming\uv\data\python\cpython-3.9.19-windows-x86_64-none\python.exe
```
test on uv 0.2.33 (build from
257007ccaf)
### Stable version
``uv venv -p 3.10`` is ``3.10.11`` (System Python)
``uv venv -p 3.9`` is ``No interpreter found``(3.9.19 for managed
Python)
``uv venv -p 3.9 --python-preference only-system`` is ``No interpreter
found``(fail)
``uv venv -p 3.9 --python-preference only-managed`` is
``3.9.19``(success)
Do not use managed Python, only use the system Python, so it can be
determined as ``only-system``.
### Preview mode
**Note:** ``3.10.14`` is managed python, ``3.10.11`` is system python.
``uv venv -p 3.11 --preview`` is ``3.11.9`` (System Python)
``uv venv -p 3.10 --preview`` is ``3.10.14``
``uv venv -p 3.10 --preview --python-preference only-managed`` is
``3.10.14``
``uv venv -p 3.10 --preview --python-preference managed`` is ``3.10.14``
``uv venv -p 3.10 --preview --python-preference system`` is ``3.10.11``
``venv -p 3.10 --preview --python-preference only-system`` is
``3.10.11``
Prioritize the managed Python and then select the system Python, so it
can be determined as ``managed``.
-----
fixed#5754
## Test Plan
Run website in local.
Zanie Blue
Ahmed Ilyas
Charlie Marsh
Delgan
FishAlchemist