Early warning: addition of hierarchical user and built-in categories
A number of changes to the tag browser have been committed to trunk. If you manipulate user categories or tag browser items directly, you might be affected.
Change 1: user categories support sub-categories. If you have a category named A, another named A.B, and another named A.C, B and C will appear as subcategories of A. If you are manipulating the db pref 'user_categories', then you probably don't care about this, because the tree view is rebuilt from that dict. You will definitely care if you want to display the item hierarchy.
Change 2: non-user categories can support hierarchies. For example, assume you have a custom col (text mult) named Genre. If you have the following items in that category:
they will display as a tree. The outermost level will contain Cooking and Mystery. Cooking will contain 1 expandable category, French, which contains two leaf nodes.
Hierarchical processing is enabled for individual categories in preferences.look & feel.
You probably will care about this change only if your plugin (or what-have-you) wants to manipulate these items in a similar way. If not, then you can continue to use the full values (as in A.B.C) and the tag browser will deal with displaying the trees.