How should I deal with pacnew?

Hello! EOS user here. I upgrade my system with topgrade, and sometimes it tells me about some pacnew files, asking if merging, replacing or removing the original ones. I snapshotted my system and tried replacing my original files (an eos-something file, where the new file changed a bunch of mirrors, and /etc/shells, where it replaced sh and bash with git-shell and zsh. After the reboot, I was unable to boot into my user account ("wrong password" but it was the correct password). I had to boot as root and restore the snapshot. I then removed that evil pacnew file.

Now my question is, how should I deal with these pacnew files? should I always remove them, always replace them, always read them and decide? I'd rather not read these things everyday, it's a bit boring, so I hope there's a better solution. How do you deal with these?