Beefed up 'Using branches' part of docs/contributing.txt

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4203 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/contributing.txt

@@ -387,21 +387,63 @@ trunk more than once.
 Using branches
 --------------
 
-To test a given branch, you can simply check out the entire branch, like so::
+To use a branch, you'll need to do two things:
+
+    * Get the branch's code through Subversion.
+
+    * Point your Python ``site-packages`` directory at the branch's version of
+      the ``django`` package rather than the version you already have
+      installed.
+
+Getting the code from Subversion
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get the latest version of a branch's code, check it out using Subversion::
 
     svn co http://code.djangoproject.com/svn/django/branches/<branch>/
 
-Or, if you've got a working directory you'd like to switch to use a branch,
-you can use::
+...where ``<branch>`` is the branch's name. See the `list of branch names`_.
+
+Alternatively, you can automatically convert an existing directory of the
+Django source code as long as you've checked it out via Subversion. To do the
+conversion, execute this command from within your ``django`` directory::
 
     svn switch http://code.djangoproject.com/svn/django/branches/<branch>/
 
-...in the root of your Django sandbox (the directory that contains ``django``,
-``docs``, and ``tests``).
-
 The advantage of using ``svn switch`` instead of ``svn co`` is that the
 ``switch`` command retains any changes you might have made to your local copy
-of the code. It attempts to merge those changes into the "switched" code.
+of the code. It attempts to merge those changes into the "switched" code. The
+disadvantage is that it may cause conflicts with your local changes if the
+"switched" code has altered the same lines of code.
+
+(Note that if you use ``svn switch``, you don't need to point Python at the new
+version, as explained in the next section.)
+
+.. _list of branch names: http://code.djangoproject.com/browser/django/branches
+
+Pointing Python at the new Django version
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Once you've retrieved the branch's code, you'll need to change your Python
+``site-packages`` directory so that it points to the branch version of the
+``django`` directory. (The ``site-packages`` directory is somewhere such as
+``/usr/lib/python2.4/site-packages`` or
+``/usr/local/lib/python2.4/site-packages`` or ``C:\Python\site-packages``.)
+
+The simplest way to do this is by renaming the old ``django`` directory to
+``django.OLD`` and moving the trunk version of the code into the directory
+and calling it ``django``.
+
+Alternatively, you can use a symlink called ``django`` that points to the
+location of the branch's ``django`` package. If you want to switch back, just
+change the symlink to point to the old code.
+
+If you're using Django 0.95 or earlier and installed it using
+``python setup.py install``, you'll have a directory called something like
+``Django-0.95-py2.4.egg`` instead of ``django``. In this case, edit the file
+``setuptools.pth`` and remove the line that references the Django ``.egg``
+file. Then copy the branch's version of the ``django`` directory into
+``site-packages``.
 
 Official releases
 =================