Added bullet to docs/contributing.txt about creating diffs from the top-level trunk directory

git-svn-id: http://code.djangoproject.com/svn/django/trunk@6078 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/contributing.txt

@@ -122,6 +122,11 @@ Patch style
       English than in code. Indentation is the most common example; it's hard to
       read patches when the only difference in code is that it's indented.
 
+	* When creating patches, always run ``svn diff`` from the top-level
+	  ``trunk`` directory -- i.e., the one that contains ``django``, ``docs``,
+	  ``tests``, ``AUTHORS``, etc. This makes it easy for other people to apply
+	  your patches.
+
     * Attach patches to a ticket in the `ticket tracker`_, using the "attach file"
       button. Please *don't* put the patch in the ticket description or comment
       unless it's a single line patch.