twbs/bootstrap — pull request #13255 by amitkeret (2014-04-01 22:46:34+00:00)
Title: Added "collapseown" functionality to $.fn.collapse()

This is intended to solve the annoyance where you click the heading of an already-opened accordion panel, causing the last visible panel to collapse and the accordion to effectively close completely.

This option makes it possible to configure the accordion in a way that will make sure there's always one visible item.