bug#21852: Ediff 2.81.5 of July 4, 2013; ediff-patch-buffer fails if patch-buf doesn't exists.

[Tino Calancha <f92capac@gmail.com>]

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-----------------------------------------------------------

ediff-patch-buffer fails if patch-buf doesn't exists.

* lisp/vc/ediff.el (ediff-patch-buffer): Added 'require-match
argument on read-buffer call.

emacs -Q:
(in the *scratch* buffer)

(with-current-buffer (generate-new-buffer "buff")
   (insert "foo bar"))

(with-current-buffer (generate-new-buffer "buff2")
   (insert "foo baz"))

;; call ediff-buffers on "buff" and "buff2" and save the
;; differences in a buffer "patch"

M-x epatch-buffer y patch RET buff ; ok
M-x epatch-buffer y patch RET buffer ; BAD
You have killed a vital Ediff buffer---you must leave Ediff now!


Emacs  : GNU Emacs 25.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.28)
  of 2015-11-07
Package: Ediff 2.81.5 of July 4, 2013

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diff --git a/lisp/vc/ediff.el b/lisp/vc/ediff.el
index 3a2d1e4..8723c19 100644
--- a/lisp/vc/ediff.el
+++ b/lisp/vc/ediff.el
@@ -1403,7 +1403,7 @@ ediff-patch-buffer
    patch-buf
    (read-buffer
     "Which buffer to patch? "
-    (ediff-other-buffer patch-buf))))
+    (ediff-other-buffer patch-buf) 'require-match)))
 
 
 ;;;###autoload