Fix bug #11490

Correctly add the branch name suffix when the stem
of the filename contains a dot.

(cherry picked from commit c3b9504835)

src/Buffer.cpp

@@ -824,10 +824,9 @@ FileName Buffer::Impl::exportFileName() const
 	if (branch_suffix.empty())
 		return filename;
 
-	string const name = filename.onlyFileNameWithoutExt()
-		+ to_utf8(branch_suffix);
+	string const name = addExtension(filename.onlyFileNameWithoutExt()
+			+ to_utf8(branch_suffix), filename.extension());
 	FileName res(filename.onlyPath().absFileName() + "/" + name);
-	res.changeExtension(filename.extension());
 
 	return res;
 }

status.23x

@@ -97,6 +97,9 @@ What's new
 - Fix LaTeX error caused by Control key shortcut inset on the Mac (remainder
   of bug 10641).
 
+- Correctly add the branch name suffix when the stem of the filename
+  contains a dot (bug 11490).
+
 
 * USER INTERFACE