Ack: don't search in the "log" directory

It tends to have a lot of crap in there that can slow down searching
quite a bit.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Vim: disable folding when viewing diffs

This sometimes happens when doing things like `e` in a `git add --patch`
run; you get dropped into an editor and have a bunch of unwelcome folds
that you end up getting rid of immediately.

Signed-off-by: Wincent Colaiuta <win@wincent.com>