vc-git: Support `diff-switches'.

Fix bug#19099.
* lisp/vc/vc-git.el (vc-git-diff): Use "difftool -x diff" with
  `diff-switches' if `vc-git-diff-switches' is nil.

2 files changed, 18 insertions, 5 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 8b7f62a306e..25ef3b3be71 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2014-11-19  Rüdiger Sonderfeld  <ruediger@c-plusplus.net>
+
+        Fix bug#19099.
+        * vc/vc-git.el (vc-git-diff): Use "difftool -x diff" with
+        `diff-switches' if `vc-git-diff-switches' is nil.
+
 2014-11-18  Juri Linkov  <juri@linkov.net>
 
         * simple.el (next-line-or-history-element): Wrap next-line
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index be0211c1132..3b11a3cd635 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -994,11 +994,18 @@ or BRANCH^ (where \"^\" can be repeated)."
 (defun vc-git-diff (files &optional rev1 rev2 buffer)
   "Get a difference report using Git between two revisions of FILES."
   (let (process-file-side-effects)
-    (apply #'vc-git-command (or buffer "*vc-diff*") 1 files
-           (if (and rev1 rev2) "diff-tree" "diff-index")
-           "--exit-code"
-           (append (vc-switches 'git 'diff)
-                   (list "-p" (or rev1 "HEAD") rev2 "--")))))
+    (if vc-git-diff-switches
+        (apply #'vc-git-command (or buffer "*vc-diff*") 1 files
+               (if (and rev1 rev2) "diff-tree" "diff-index")
+               "--exit-code"
+               (append (vc-switches 'git 'diff)
+                       (list "-p" (or rev1 "HEAD") rev2 "--")))
+      (vc-git-command (or buffer "*vc-diff*") 1 files
+                      "difftool" "--exit-code" "--no-prompt" "-x"
+                      (concat "diff "
+                              (mapconcat 'identity
+                                         (vc-switches nil 'diff) " "))
+                      (or rev1 "HEAD") rev2 "--"))))
 
 (defun vc-git-revision-table (_files)
   ;; What about `files'?!?  --Stef