(Format Conversion Round-Trip): Improve previous change.

doc/lispref/ChangeLog

+2008-11-28  Glenn Morris  <rgm@gnu.org>
+
+	* files.texi (Format Conversion Round-Trip): Improve previous change.
+
 2008-11-26  Chong Yidong  <cyd@stupidchicken.com>
 
 	* modes.texi (Auto Major Mode): Fix example.

doc/lispref/files.texi

@@ -2985,8 +2985,9 @@ in the order of appearance in the list.
 This command writes the current buffer contents into the file
 @var{file} in format @var{format}, and makes that format the default
 for future saves of the buffer.  That is, it sets the buffer-local value
-of @code{buffer-file-format} to @var{format}, and replaces any existing
-elements (except any with a non-nil @var{preserve} flag; see above).
+of @code{buffer-file-format} to @var{format}.  It then appends any
+elements of the previous value with a non-nil @var{preserve} flag (see
+above), if they are not already present in the new value.
 The argument @var{format} is a list of format names.
 Except for the @var{format} argument, this command
 is similar to @code{write-file}.  In particular, @var{confirm} has the