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, 20 insertions, 25 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6ecce26be14..92d90accc60 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2014-08-11  Glenn Morris  <rgm@gnu.org>
+
+        * fileio.c: 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.)
+        (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.
+
 2014-08-09  Martin Rudalics  <rudalics@gmx.at>
 
         * window.c (Fwindow_new_total, Fwindow_new_normal)
diff --git a/src/fileio.c b/src/fileio.c
index c87a6f71312..261928dd821 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -323,7 +323,6 @@ static Lisp_Object Qfile_acl;
 static Lisp_Object Qset_file_acl;
 static Lisp_Object Qfile_newer_than_file_p;
 Lisp_Object Qinsert_file_contents;
-static Lisp_Object Qchoose_write_coding_system;
 Lisp_Object Qwrite_region;
 static Lisp_Object Qverify_visited_file_modtime;
 static Lisp_Object Qset_visited_file_modtime;
@@ -4531,24 +4530,14 @@ build_annotations_unwind (Lisp_Object arg)
 
 /* Decide the coding-system to encode the data with.  */
 
-DEFUN ("choose-write-coding-system", Fchoose_write_coding_system,
-       Schoose_write_coding_system, 3, 6, 0,
-       doc: /* Choose the coding system for writing a file.
-Arguments are as for `write-region'.
-This function is for internal use only.  It may prompt the user.  */ )
-  (Lisp_Object start, Lisp_Object end, Lisp_Object filename,
-   Lisp_Object append, Lisp_Object visit, Lisp_Object lockname)
+static Lisp_Object
+choose_write_coding_system (Lisp_Object start, Lisp_Object end, Lisp_Object filename,
+                            Lisp_Object append, Lisp_Object visit, Lisp_Object lockname,
+                            struct coding_system *coding)
 {
   Lisp_Object val;
   Lisp_Object eol_parent = Qnil;
 
-  /* Mimic write-region behavior.  */
-  if (NILP (start))
-    {
-      XSETFASTINT (start, BEGV);
-      XSETFASTINT (end, ZV);
-    }
-
   if (auto_saving
       && NILP (Fstring_equal (BVAR (current_buffer, filename),
                               BVAR (current_buffer, auto_save_file_name))))
@@ -4641,6 +4630,10 @@ This function is for internal use only.  It may prompt the user.  */ )
     }
 
   val = coding_inherit_eol_type (val, eol_parent);
+  setup_coding_system (val, coding);
+
+  if (!STRINGP (start) && !NILP (BVAR (current_buffer, selective_display)))
+    coding->mode |= CODING_MODE_SELECTIVE_DISPLAY;
   return val;
 }
 
@@ -4809,14 +4802,9 @@ write_region (Lisp_Object start, Lisp_Object end, Lisp_Object filename,
      We used to make this choice before calling build_annotations, but that
      leads to problems when a write-annotate-function takes care of
      unsavable chars (as was the case with X-Symbol).  */
-  Vlast_coding_system_used =
-    Fchoose_write_coding_system (start, end, filename,
-                                 append, visit, lockname);
-
-  setup_coding_system (Vlast_coding_system_used, &coding);
-
-  if (!STRINGP (start) && !NILP (BVAR (current_buffer, selective_display)))
-    coding.mode |= CODING_MODE_SELECTIVE_DISPLAY;
+  Vlast_coding_system_used
+    = choose_write_coding_system (start, end, filename,
+                                 append, visit, lockname, &coding);
 
 #ifdef CLASH_DETECTION
   if (open_and_close_file && !auto_saving)
@@ -5861,7 +5849,6 @@ syms_of_fileio (void)
   DEFSYM (Qset_file_acl, "set-file-acl");
   DEFSYM (Qfile_newer_than_file_p, "file-newer-than-file-p");
   DEFSYM (Qinsert_file_contents, "insert-file-contents");
-  DEFSYM (Qchoose_write_coding_system, "choose-write-coding-system");
   DEFSYM (Qwrite_region, "write-region");
   DEFSYM (Qverify_visited_file_modtime, "verify-visited-file-modtime");
   DEFSYM (Qset_visited_file_modtime, "set-visited-file-modtime");
@@ -6100,7 +6087,6 @@ This includes interactive calls to `delete-file' and
   defsubr (&Sdefault_file_modes);
   defsubr (&Sfile_newer_than_file_p);
   defsubr (&Sinsert_file_contents);
-  defsubr (&Schoose_write_coding_system);
   defsubr (&Swrite_region);
   defsubr (&Scar_less_than_car);
   defsubr (&Sverify_visited_file_modtime);