reciprocity/ggrc-core — pull request #1415 by Smotko (2014-06-05 14:40:38+00:00)
Title: Bugfix: Make sure objects can't be mapped to themselves

On of the reasons why this story got rejected: https://www.pivotaltracker.com/story/show/71468034

The other one is that the map link shows up for mappings that should not be possible (mapping program to program).