bjorn/tiled — pull request #170 by stefanbeller (2012-03-18 20:01:57+00:00)
Title: When exporting, use map name as default 

When exporting a map to a custom format,
the basename of the maps filename is kept and only
the extension is replaced as a proposal of the
file dialog.

The solution as provided here
https://sourceforge.net/apps/mantisbt/tiled/view.php?id=86
does not add the correct file extension.