Insert extra new line at the end of the files

[OpenDog]

Could you please insert an additional newline at the end of each concatenated file? Sometimes, people (like me) forget to include a '\n' at the end of the file, which can result in random errors (invalid concatenated file). For instance, if the file ends with a comment, and you continue with the next file, the first line might unintentionally become part of the comment. This issue is quasi-random and depends on the file order.

[thgh]

Sure, PR welcome!