localrepo: use the vfs join method to implement the localrepo join method This will make it possible to customize the behavior of the join method by changing the vfs class (e.g. by using the altvfs" class introduced recently). Note that we could have modified the VFS join methods to acept a set of optional paths in the same way thta the localrepo join method does. However it seemed simpler to simply call os.path.join before calling self.vfs.join.