Add uv python install --default (#8650)

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Adds a `--default` flag to `uv python install` in preview. This includes
a `python` and `python{major}` executable in addition to the
`python{major}.{minor}` executable. We will replace uv-managed
executables, but externally managed executables require the `--force`
flag to overwrite.

If you run `uv python install` (without arguments), we include the
`--default` flag implicitly to populate `python` and `python3` for the
"default" install version.

In the future, we should add a warning if the installed executable isn't
at the front of the PATH.

Author: zanieb

crates/uv-cli/src/lib.rs

@@ -4226,6 +4226,21 @@ pub struct PythonInstallArgs {
     /// Implies `--reinstall`.
     #[arg(long, short)]
     pub force: bool,
+
+    /// Use as the default Python version.
+    ///
+    /// By default, only a `python{major}.{minor}` executable is installed, e.g., `python3.10`. When
+    /// the `--default` flag is used, `python{major}`, e.g., `python3`, and `python` executables are
+    /// also installed.
+    ///
+    /// Alternative Python variants will still include their tag. For example, installing
+    /// 3.13+freethreaded with `--default` will include in `python3t` and `pythont`, not `python3`
+    /// and `python`.
+    ///
+    /// If multiple Python versions are requested during the installation, the first request will be
+    /// the default.
+    #[arg(long)]
+    pub default: bool,
 }
 
 #[derive(Args)]

crates/uv-python/src/installation.rs

@@ -327,8 +327,8 @@ impl PythonInstallationKey {
         &self.libc
     }
 
-    /// Return a canonical name for a versioned executable.
-    pub fn versioned_executable_name(&self) -> String {
+    /// Return a canonical name for a minor versioned executable.
+    pub fn executable_name_minor(&self) -> String {
         format!(
             "python{maj}.{min}{var}{exe}",
             maj = self.major,
@@ -337,6 +337,25 @@ impl PythonInstallationKey {
             exe = std::env::consts::EXE_SUFFIX
         )
     }
+
+    /// Return a canonical name for a major versioned executable.
+    pub fn executable_name_major(&self) -> String {
+        format!(
+            "python{maj}{var}{exe}",
+            maj = self.major,
+            var = self.variant.suffix(),
+            exe = std::env::consts::EXE_SUFFIX
+        )
+    }
+
+    /// Return a canonical name for an un-versioned executable.
+    pub fn executable_name(&self) -> String {
+        format!(
+            "python{var}{exe}",
+            var = self.variant.suffix(),
+            exe = std::env::consts::EXE_SUFFIX
+        )
+    }
 }
 
 impl fmt::Display for PythonInstallationKey {