Allow smerge-keep-current to work for empty hunks

Bug#25555
* lisp/vc/smerge-mode.el (smerge-get-current): Allow point to be at
match-end.
* test/lisp/vc/smerge-mode-tests.el: New file.

lisp/vc/smerge-mode.el

@@ -725,7 +725,7 @@ this keeps \"UUU\"."
   (let ((i 3))
     (while (or (not (match-end i))
 	       (< (point) (match-beginning i))
-	       (>= (point) (match-end i)))
+	       (> (point) (match-end i)))
       (cl-decf i))
     i))
 

test/lisp/vc/smerge-mode-tests.el

+;; Copyright (C) 2017  Free Software Foundation, Inc
+
+;; Maintainer: emacs-devel@gnu.org
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'smerge-mode)
+
+(ert-deftest smerge-mode-test-empty-hunk ()
+  "Regression test for bug #25555"
+  (with-temp-buffer
+    (insert "<<<<<<< one\n")
+    (save-excursion
+      (insert "=======\nLLL\n>>>>>>> end\n"))
+    (smerge-mode)
+    (smerge-keep-current)
+    (should (equal (buffer-substring (point-min) (point-max)) ""))))
+
+(provide 'smerge-mode-tests)