Variable: diff-switches
diff-switches is a customizable variable defined in diff.el.gz.
Value
"-u"
Documentation
A string or list of strings specifying switches to be passed to diff.
This variable is also used in the vc-diff command (and related
commands) if the backend-specific diff switch variable isn't
set (vc-git-diff-switches for git, for instance), and
vc-diff-switches isn't set.
Probably introduced at or before Emacs version 19.1.
Source Code
;; Defined in /usr/src/emacs/lisp/vc/diff.el.gz
;;;###autoload
(defcustom diff-switches "-u"
"A string or list of strings specifying switches to be passed to diff.
This variable is also used in the `vc-diff' command (and related
commands) if the backend-specific diff switch variable isn't
set (`vc-git-diff-switches' for git, for instance), and
`vc-diff-switches' isn't set."
:type '(choice string (repeat string)))