def make_tmpname(basename, n)
      extension = File.extname(basename)
      sprintf("%s,%d,%d%s", File.basename(basename, extension), $$, n.to_i, extension)
    end
def make_tmpname(basename, n)
      extension = File.extname(basename)
      sprintf("%s,%d,%d%s", File.basename(basename, extension), $$, n.to_i, extension)
    end
Replaces Tempfile's +make_tmpname+ with one that honors file extensions.
 Copied from Paperclip