jashkenas/backbone — pull request #2744 by JoeWagner (2013-09-06 22:07:37+00:00)
Title: Optionally let collection.set keep unsynced models

I would like to optionally specify that collection.set should not remove models that have not finished saving to the server.
Specifically calling fetch and updating the client with any changes that exist on the server, will cause any models that are in the process of being saved to be removed on the client.