[arch-general] Apppearance of .pacnew files

Hi, I've got a question about the appearance of .pacnew files. I've got two servers running archlinux, and I did pacman's 4.0.3 upgrade on both. The first server did the upgrade as expected, creating the pacman.conf.pacnew file. The second server merge my file with the new one, without asking for anything ! So here comes my question: how is it resolved that a file must be replaced (2nd case) or created as .pacnew ? Sorry for my poor English G.