spree/spree — pull request #1323 by alekseydem (2012-03-28 21:55:25+00:00)
Title: Don't set count_on_hand to zero when not all backorders filled

A little strange Spree behavior with track_inventory_levels == true.

count_on_hand = -10

on_hand = 15 -> count_on_hand becomes 5. Good.
But: on_hand = 5 -> count_on_hand becomes 0. Not -5

Seems it should keep count_on_hand negative when count is not enough to fill backorders