- ;; If rev1 is nil, `diff' uses the current workfile version.
- (zerop (vc-call diff file)))
+ (zerop (condition-case err
+ ;; If the implementation supports it, let the output
+ ;; go to *vc*, not *vc-diff*, since this is an internal call.
+ (vc-call diff file nil nil "*vc*")
+ (wrong-number-of-arguments
+ ;; If this error came from the above call to vc-BACKEND-diff,
+ ;; try again without the optional buffer argument (for
+ ;; backward compatibility). Otherwise, resignal.
+ (if (or (not (eq (cadr err)
+ (indirect-function
+ (vc-find-backend-function (vc-backend file)
+ 'diff))))
+ (not (eq (caddr err) 4)))
+ (signal (car err) (cdr err))
+ (vc-call diff file))))))