Fixed #15208 - Document ModelAdmin.formfield_for_choice_field; thanks julien.

                    kwargs["queryset"] = Car.objects.filter(owner=request.user)

                return super(MyModelAdmin, self).formfield_for_manytomany(db_field, request, **kwargs)

.. method:: ModelAdmin.formfield_for_choice_field(self, db_field, request, **kwargs)

    Like the ``formfield_for_foreignkey`` and ``formfield_for_manytomany``

    methods, the ``formfield_for_choice_field`` method can be overridden to

    change the default formfield for a field that has declared choices. For

    example, if the choices available to a superuser should be different than

    those available to regular staff, you could proceed as follows::

        class MyModelAdmin(admin.ModelAdmin):

            def formfield_for_choice_field(self, db_field, request, **kwargs):

                if db_field.name == "status":

                    kwargs['choices'] = (

                        ('accepted', 'Accepted'),

                        ('denied', 'Denied'),

                    )

                    if request.user.is_superuser:

                        kwargs['choices'] += (('ready', 'Ready for deployment'),)

                return super(MyModelAdmin, self).formfield_for_choice_field(db_field, request, **kwargs)

.. method:: ModelAdmin.has_add_permission(self, request)

    Should return ``True`` if adding an object is permitted, ``False``