docs: udpate package_discovery.txt

docs/userguide/package_discovery.txt

@@ -2,15 +2,27 @@
 Package Discovery
 ===================
 
+``Setuptools`` provide powerful tools to handle package discovery, including
+support for namespace package. The following explain how you include package
+in your ``setup`` script::
+
+    setup(
+        packages = ['mypkg1', 'mypkg2']
+    )
+
+To speed things up, we introduce two functions provided by setuptools::
+
+    from setuptools import find_packages
+
+or::
+
+    from setuptools import find_namespace_packages
 
 
 Using ``find_packages()``
 -------------------------
 
-For simple projects, it's usually easy enough to manually add packages to
-the ``packages`` argument of ``setup()``.  However, for very large projects
-(Twisted, PEAK, Zope, Chandler, etc.), it can be a big burden to keep the
-package list updated.  That's what ``setuptools.find_packages()`` is for.
+Let's start with the first tool.
 
 ``find_packages()`` takes a source directory and two lists of package name
 patterns to exclude and include.  If omitted, the source directory defaults to
@@ -166,4 +178,4 @@ You must include the ``declare_namespace()``  line in the ``__init__.py`` of
 order to ensure that the namespace will be declared regardless of which
 project's copy of ``__init__.py`` is loaded first.  If the first loaded
 ``__init__.py`` doesn't declare it, it will never *be* declared, because no
-other copies will ever be loaded!
\ No newline at end of file
+other copies will ever be loaded!