Fix bug #4451.

 vc.el (vc-coding-system-inherit-eol): New defvar.
 (vc-coding-system-for-diff): Use it to decide whether to inherit
 from the file the EOL format for reading the diffs of that file.

2 files changed, 23 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index bdbc96a5afe..0ce0e8e3073 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2010-07-16  Reiner Steib  <Reiner.Steib@gmx.de>
+
+        * vc.el (vc-coding-system-inherit-eol): New defvar.
+        (vc-coding-system-for-diff): Use it to decide whether to inherit
+        from the file the EOL format for reading the diffs of that file.
+        (Bug#4451)
+
 2010-07-16  Eli Zaretskii  <eliz@gnu.org>
 
         * mail/rmailmm.el (rmail-mime-save): Make the temp buffer
diff --git a/lisp/vc.el b/lisp/vc.el
index 194c2a08983..a7d4ec66391 100644
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -1398,6 +1398,16 @@ Runs the normal hooks `vc-before-checkin-hook' and `vc-checkin-hook'."
 ;;          (vc-call-backend ',(vc-backend f)
 ;;                           'diff (list ',f) ',rev1 ',rev2))))))
 
+(defvar vc-coding-system-inherit-eol t
+  "When non-nil, inherit the EOL format for reading Diff output from the file.
+
+Used in `vc-coding-system-for-diff' to determine the EOL format to use
+for reading Diff output for a file.  If non-nil, the EOL format is
+inherited from the file itself.
+Set this variable to nil if your Diff tool might use a different
+EOL.  Then Emacs will auto-detect the EOL format in Diff output, which
+gives better results.") ;; Cf. bug#4451.
+
 (defun vc-coding-system-for-diff (file)
   "Return the coding system for reading diff output for FILE."
   (or coding-system-for-read
@@ -1405,7 +1415,12 @@ Runs the normal hooks `vc-before-checkin-hook' and `vc-checkin-hook'."
       ;; use the buffer's coding system
       (let ((buf (find-buffer-visiting file)))
         (when buf (with-current-buffer buf
-                    buffer-file-coding-system)))
+                    (if vc-coding-system-inherit-eol
+                        buffer-file-coding-system
+                      ;; Don't inherit the EOL part of the coding-system,
+                      ;; because some Diff tools may choose to use
+                      ;; a different one.  bug#4451.
+                      (coding-system-base buffer-file-coding-system)))))
       ;; otherwise, try to find one based on the file name
       (car (find-operation-coding-system 'insert-file-contents file))
       ;; and a final fallback