replace command cp with cp for POSIX-guaranteed utility

setup/init.sh

@@ -282,7 +282,7 @@ command find -- . -type d -empty \
 # if sed installation was successful, and
 # if zsh is available, replace bash, ash, and sh with zsh in `/etc/passwd`
 command -v zsh >/dev/null 2>&1 && command grep -E '/bin/b?a?sh' /etc/passwd 2>&1 &&
-  command cp -- /etc/passwd /etc/passwd-"$(command date '+%Y%m%d')" &&
+  cp -- /etc/passwd /etc/passwd-"$(command date '+%Y%m%d')" &&
   # `-i` for in-place editing
   # `-E` for regex searching for `/bin/ash` and `/bin/sh`
   command sed -i -E "s|/bin/b?a?sh$|$(command -v zsh)|g" /etc/passwd