bug#23436: [PATCH] Use the true name of a file to determine responsible vc.

[Hong Xu]

In many cases, e.g., a symbolic link to a directory inside a vc tracked
directory, vc-responsible-backend would fail to know the true backend.

---

There is probably a better fix than this... Feel free to do so.

---
 lisp/vc/vc.el | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 25b41e34e645..1b060b4d1374 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -960,14 +960,15 @@ If FILE is already registered, return the
 backend of FILE.  If FILE is not registered, then the
 first backend in `vc-handled-backends' that declares itself
 responsible for FILE is returned."
-  (or (and (not (file-directory-p file)) (vc-backend file))
+  (let ((file-path (file-truename file)))
+    (or (and (not (file-directory-p file-path)) (vc-backend file-path))
       (catch 'found
-       ;; First try: find a responsible backend.  If this is for registration,
-       ;; it must be a backend under which FILE is not yet registered.
-       (dolist (backend vc-handled-backends)
-         (and (vc-call-backend backend 'responsible-p file)
-              (throw 'found backend))))
-      (error "No VC backend is responsible for %s" file)))
+        ;; First try: find a responsible backend.  If this is for registration,
+        ;; it must be a backend under which FILE is not yet registered.
+        (dolist (backend vc-handled-backends)
+          (and (vc-call-backend backend 'responsible-p file-path)
+            (throw 'found backend))))
+      (error "No VC backend is responsible for %s" file-path))))
 
 (defun vc-expand-dirs (file-or-dir-list backend)
   "Expands directories in a file list specification.
-- 
2.8.2