Fixed #6891 -- Clarified modelform usage documentation. Thanks to Eri…

…c Holscher for the suggestion.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7728 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/modelforms.txt

@@ -182,6 +182,13 @@ supplied, ``save()`` will update that instance. If it's not supplied,
     # Create a form to edit an existing Article.
     >>> a = Article.objects.get(pk=1)
     >>> f = ArticleForm(instance=a)
+    >>> f.save()
+
+    # Create a form to edit an existing Article, but use
+    # POST data to populate the form.
+    >>> a = Article.objects.get(pk=1)
+    >>> f = ArticleForm(request.POST, instance=a)
+    >>> f.save()
 
 Note that ``save()`` will raise a ``ValueError`` if the data in the form
 doesn't validate -- i.e., ``if form.errors``.