vc-disable-async-diff: Don't bind when it's undefined

Fixes #47

diff --git a/diff-hl.el b/diff-hl.el
index 5b6510d557c62e9f398350f928889094ecf69ec2..8f2221a7c0ee399488b8f0c1375eeff86315722f 100644 (file)
--- a/diff-hl.el
+++ b/diff-hl.el
@@ -213,7 +213,8 @@
          (vc-hg-diff-switches nil)
          (vc-svn-diff-switches nil)
          (vc-diff-switches '("-U0"))
-         (vc-disable-async-diff t))
+         ,@(when (boundp 'vc-disable-async-diff)
+             '((vc-disable-async-diff t))))
      ,body))
 
 (defun diff-hl-changes ()