docs: add docs to uv python pin without a REQUEST argument (#9631)

Co-authored-by: Zanie Blue <[email protected]>

crates/uv-cli/src/lib.rs

@@ -4159,8 +4159,12 @@ pub enum PythonCommand {
 
     /// Pin to a specific Python version.
     ///
-    /// Writes the pinned version to a `.python-version` file, which is then
-    /// read by other uv commands when determining the required Python version.
+    /// Writes the pinned Python version to a `.python-version` file, which is used by other uv
+    /// commands to determine the required Python version.
+    ///
+    /// If no version is provided, uv will look for an existing `.python-version` file and display
+    /// the currently pinned version. If no `.python-version` file is found, uv will exit with an
+    /// error.
     ///
     /// See `uv help python` to view supported request formats.
     Pin(PythonPinArgs),
@@ -4339,6 +4343,8 @@ pub struct PythonPinArgs {
     /// files, i.e., `pyenv`. If compatibility with those tools is needed, only
     /// use version numbers instead of complex requests such as `[email protected]`.
     ///
+    /// If no request is provided, the currently pinned version will be shown.
+    ///
     /// See `uv help python` to view supported request formats.
     pub request: Option<String>,
 

docs/reference/cli.md

@@ -4771,7 +4771,9 @@ uv python find [OPTIONS] [REQUEST]
 
 Pin to a specific Python version.
 
-Writes the pinned version to a `.python-version` file, which is then read by other uv commands when determining the required Python version.
+Writes the pinned Python version to a `.python-version` file, which is used by other uv commands to determine the required Python version.
+
+If no version is provided, uv will look for an existing `.python-version` file and display the currently pinned version. If no `.python-version` file is found, uv will exit with an error.
 
 See `uv help python` to view supported request formats.
 
@@ -4787,6 +4789,8 @@ uv python pin [OPTIONS] [REQUEST]
 
 <p>uv supports more formats than other tools that read <code>.python-version</code> files, i.e., <code>pyenv</code>. If compatibility with those tools is needed, only use version numbers instead of complex requests such as <code>[email protected]</code>.</p>
 
+<p>If no request is provided, the currently pinned version will be shown.</p>
+
 <p>See <a href="#uv-python">uv python</a> to view supported request formats.</p>
 
 </dd></dl>