Variable: diff-default-directory
diff-default-directory is a buffer-local variable defined in
diff-mode.el.gz.
Documentation
The default directory where the current Diff buffer was created.
Source Code
;; Defined in /usr/src/emacs/lisp/vc/diff-mode.el.gz
(defvar-local diff-default-directory nil
"The default directory where the current Diff buffer was created.")