Comment 6 for bug 488594

In gnome bugzilla Paolo Borelli sais:

this is probably due to the fact that gio does not report them as "text" files,
if you right click on the file browser and select filter->show binary they
should be listed.

To fix it properly the mime type database of freedesktop's shared-mime-info
should report them as descendants of text/plain mime type.

Thanks!