Fixed #8639; documented the fact that the "startproject" command is invalid when…

Fixed #8639; documented the fact that the "startproject" command is invalid when fed an existing project's settings


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8740 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/django-admin.txt

@@ -645,6 +645,12 @@ startproject <projectname>
 Creates a Django project directory structure for the given project name in the
 current directory.
 
+This command is disabled when the ``--settings`` option to
+``django-admin.py`` is used, or when the environment variable
+``DJANGO_SETTINGS_MODULE`` has been set. To re-enable it in these
+situations, either omit the ``--settings`` option or unset
+``DJANGO_SETTINGS_MODULE``.
+
 syncdb
 ------