branches: change handling again, but this time a little less magic. This change means that files located in the actual branches directory will now be wholly ignored. If we want to handle those correctly, it will take a reasonably large amount of work and probably a configuration flag. Also, any non-related paths outside of branches/trunk will be explicitly ignored, which is similar to the somewhat accidental pre-branch-refactor behavior. Finally, any unrelated files located as children of branches will cause the directory in branches to be used as the branch - not, as recently was the case, the directory immediately containing that file.