Add pip completion documentation

docs/html/cli/index.md

@@ -30,6 +30,13 @@ pip_check
 pip_lock
 ```
 
+```{toctree}
+:maxdepth: 1
+:caption: Command-line usability and shell integration
+
+pip_completion
+```
+
 ```{toctree}
 :maxdepth: 1
 :caption: Handling Distribution Files

docs/html/cli/pip_completion.rst

@@ -0,0 +1,72 @@
+.. _`pip completion`:
+
+==============
+pip completion
+==============
+
+
+Usage
+=====
+
+.. tab:: Unix/macOS
+
+   .. pip-command-usage:: completion "python -m pip"
+
+.. tab:: Windows
+
+   .. pip-command-usage:: completion "py -m pip"
+
+
+Description
+===========
+
+.. pip-command-description:: completion
+
+Options
+=======
+
+.. pip-command-options:: completion
+
+
+Example Setups
+==============
+
+Enable pip tab completion in your shell:
+
+.. tab:: Bash
+
+   Add the following line to your ~/.bashrc:
+
+   .. code-block:: console
+
+      echo 'eval "$(python -m pip completion --bash)"' >> ~/.bashrc
+
+   Then reload your shell or run ``source ~/.bashrc`` to enable it immediately.
+
+.. tab:: Zsh
+
+   Add the following line to your ~/.zshrc:
+
+   .. code-block:: console
+
+      echo 'eval "$(python -m pip completion --zsh)"' >> ~/.zshrc
+
+   Reload your shell or run ``source ~/.zshrc``.
+
+.. tab:: PowerShell
+
+   Add the following line to your PowerShell profile:
+
+   .. code-block:: powershell
+
+      python -m pip completion --powershell | Out-String | Invoke-Expression
+
+   Restart your PowerShell session for the changes to take effect.
+
+   .. note::
+
+      On Windows, ``pip.exe`` may point to a specific Python installation
+      (e.g. ``C:\Users\<user>\AppData\Local\Programs\Python\Python313\python.exe -m pip``).
+      In this case, tab completion works for that exact command. To enable
+      completion for the ``pip`` command itself in PowerShell, you can use
+      ``Register-ArgumentCompleter`` with ``CommandName pip``.

news/13536.doc.rst

@@ -0,0 +1 @@
+Add ``pip completion`` documentation.

src/pip/_internal/commands/completion.py

@@ -81,6 +81,8 @@ class CompletionCommand(Command):
     """A helper command to be used for command completion."""
 
     ignore_require_venv = True
+    usage = """
+      %prog [options]"""
 
     def add_options(self) -> None:
         self.cmd_opts.add_option(