Draft: Example of how to use remove-on-upgrade for compat file
In the future, upstream might get rid of the compatibility/deprecation file /etc/bash_completion.d/000_bash_completion_compat.bash. When that happens the Debian package should remove the file from /etc, but using remove-on-upgrade so that the user gets warned if they had made local changes to the file. Also, the modified file would be saved as /etc/bash_completion.d/000_bash_completion_compat.bash.dpkg-old.