Fixed -- Doc'd that ModelAdmin.prepopulated_fields only works on add forms.
@@ -1044,6 +1044,10 @@ subclass::
of the source fields, and then by transforming that result into a valid
slug (e.g. substituting dashes for spaces).
+ Fields are prepopulated on add forms but not on change forms. It's usually
+ undesired that slugs change after an object is created (which would cause
+ an object's URL to change if the slug is used in it).
+
``prepopulated_fields`` doesn't accept ``DateTimeField``, ``ForeignKey``,
``OneToOneField``, and ``ManyToManyField`` fields.
