Added plugin support to the cli

docs/cli.rst

@@ -214,3 +214,37 @@ step.
     Whenever click now needs to operate on a Flask application it will
     call that function with the script info and ask for it to be created.
 4.  All is rounded up by invoking the script.
+
+CLI Plugins
+-----------
+
+Flask extensions can always patch the `Flask.cli` instance with more
+commands if they want.  However there is a second way to add CLI plugins
+to Flask which is through `setuptools`.  If you make a Python package that
+should export a Flask command line plugin you can ship a `setup.py` file
+that declares an entrypoint that points to a click command:
+
+Example `setup.py`::
+
+    from setuptools import setup
+
+    setup(
+        name='flask-my-extension',
+        ...
+        entry_points='''
+            [flask.commands]
+            my-command=mypackage.commands:cli
+        ''',
+    )
+
+Inside `mypackage/comamnds.py` you can then export a Click object::
+
+    import click
+
+    @click.command()
+    def cli():
+        """This is an example command."""
+
+Once that package is installed in the same virtualenv as Flask itself you
+can run ``flask my-command`` to invoke your command.  This is useful to
+provide extra functionality that Flask itself cannot ship.