When I 'C-x v d' my working directory in a recent Emacs, it prints "Traversing directory: ..." and goes through the whole repository. I have no idea what it looks for. After about 1 minute of waiting I C-g'd it.
It used to work instantly (well, in under 2 seconds anyway) a couple of weeks ago; don't remember more precisely.
Version: GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.9) of 2014-12-15