hmarr/mongoengine — pull request #515 by MeirKriheli (2012-06-07 09:45:47+00:00)
Title: Feature: PULL reverse_delete_rule

Using reverse_delete_rule of NULIFY or CASCADE on ListField(ReferenceField) may produce undesired results. The former will Nullify the entire field (with all the other references found in the list) while the latter will delete the entire document.

This adds another reverse_delete_rule: PULL. It just removes the reference from the list (keeping all other references intact).