joomla/joomla-platform — pull request #777 by hieblmedia (2012-01-21 19:31:48+00:00)
Title: JInstaller improvements/adjustments

1. The package adapter executes the install method twice. This can insert dublicate database entries.
See: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=27802

2. On some install adapters a check is_a($updateElement, 'JXMLElement') return always true and force an update. This is not desirable.

3. The template install adapter never return an existing extension id (setQuery was not set). This forces and update also and create dublicate database entries in the extensions table (also template styles). Updated query with exception and direct rollback.