Revert 2013-01-31 change that decides coding system before backing up

It causes a more serious problem than the one it solves.
This closes bug#18141, and reopens bug#13522.

* lisp/files.el (basic-save-buffer-2): Revert 2013-01-31 change.

* src/fileio.c: Revert 2013-01-31 change.
(choose_write_coding_system): No longer callable from Lisp.
Move last piece back here from Fwrite_region.
(Fwrite_region, syms_of_fileio): Update for above changes.

* test/automated/data/files-bug18141.el.gz: New file.
* test/automated/files.el (files-test-bug-18141-file):
New variable and test.

2 files changed, 9 insertions, 11 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index cec6e709c2b..ba8dac2c4e9 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2014-08-11  Glenn Morris  <rgm@gnu.org>
+
+        * files.el (basic-save-buffer-2): Revert 2013-01-31 change, which
+        chose coding system for writing before backing up, since it causes
+        a more serious problem than the one it solves.  (Closes Bug#18141,
+        reopens Bug#13522.)
+
 2014-08-10  Martin Rudalics  <rudalics@gmx.at>
 
         * window.el (window-total-size): Make doc-string more
diff --git a/lisp/files.el b/lisp/files.el
index 6c3b8f4fa4d..5ed5f8a6e1e 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4756,7 +4756,7 @@ Before and after saving the buffer, this function runs
 ;; This returns a value (MODES EXTENDED-ATTRIBUTES BACKUPNAME), like
 ;; backup-buffer.
 (defun basic-save-buffer-2 ()
-  (let (tempsetmodes setmodes writecoding)
+  (let (tempsetmodes setmodes)
     (if (not (file-writable-p buffer-file-name))
         (let ((dir (file-name-directory buffer-file-name)))
           (if (not (file-directory-p dir))
@@ -4772,14 +4772,6 @@ Before and after saving the buffer, this function runs
                      buffer-file-name)))
                   (setq tempsetmodes t)
                 (error "Attempt to save to a file which you aren't allowed to write"))))))
-    ;; This may involve prompting, so do it now before backing up the file.
-    ;; Otherwise there can be a delay while the user answers the
-    ;; prompt during which the original file has been renamed.  (Bug#13522)
-    (setq writecoding
-          ;; Args here should match write-region call below around
-          ;; which we use writecoding.
-          (choose-write-coding-system nil nil buffer-file-name nil t
-                                      buffer-file-truename))
     (or buffer-backed-up
         (setq setmodes (backup-buffer)))
     (let* ((dir (file-name-directory buffer-file-name))
@@ -4861,11 +4853,10 @@ Before and after saving the buffer, this function runs
                                  (logior (car setmodes) 128))))))
         (let (success)
           (unwind-protect
+              (progn
                 ;; Pass in nil&nil rather than point-min&max to indicate
                 ;; we're saving the buffer rather than just a region.
                 ;; write-region-annotate-functions may make us of it.
-              (let ((coding-system-for-write writecoding)
-                    (coding-system-require-warning nil))
                 (write-region nil nil
                               buffer-file-name nil t buffer-file-truename)
                 (setq success t))