I finally figured out the best way to do repository selection.  The whole issue I was having was finding an efficient way of selecting a repository which lies underneath a served directory.  A user may have multiple directories that can contain many repositories.  My first attempt was a NSTreeView, it failed miserably because of the sheer number of items being displayed.  My second attempt was a series of NSTableViews that would slide in or out of view based on selection, the tables would revert to the previous selection when you unselected an item.  It was a nice looking effect but when Snow Leopard came out empty NSTableView selections no longer triggered an event even with allowEmptySelection: enabled.  So my third and final attempt is a singular menu, as seen in many apps that deal with projects.  The menu shows the served directories and the repositories they contain in a drop down.  This allows easy selection and simplifies the internals of SvnXact so that I only deal with one project at a time, should also reduce memory usage