Patch Set 1: I would prefer that you didn't submit this

We already could delete more than one branch from the repository view. This patch covers the Delete dialog available from the "Advanced" menu (took me a while to figure). Please mention where this fix applies in the commit message.

Only marking a non-leaf node in the dialog will give you a StringIndexOutOfBoundsException because zero branches are selected. Don't crash or disable the Ok button when the selection does not include a ref node. 

Including a non-leaf node will give you a classcast exception. That would happen if I enter the pattern old/ to delete a bunch of obsolete branches, then "select all" and press Ok.

The dialog stays open and the exceptions are only seen in the error log (which is ok since these are programming errors anyway).

A progress indicator for massive deletes, e.g. cleaning up remote tracking branches, would be nice.