Disabled global-whitespace-mode as it makes string quoted in double quote highlighted in fundamental-mode.
https://emacs.stackexchange.com/questions/61770/whitespace-style-face-activats-highlighting-of-quoted-string-in-fundamental-mo
Old good show-trailing-whitespace is used until global-whitespace-mode is fixed.
Eliminated lags when navigating diff file cause by visiting files behind the
scene in order to get proper highlighting.
This generates calls to `vc-git-find-revision` and spawn 2 git processes. Noticeably slow on Cygwin.