Shellcheck passes once again

It prefers new lines to be escaped `\\n` and to use `command -v`
instead of `which`.

mac

@@ -8,7 +8,7 @@ fancy_echo() {
   local fmt="$1"; shift
 
   # shellcheck disable=SC2059
-  printf "\n$fmt\n" "$@"
+  printf "\\n$fmt\\n" "$@"
 }
 
 append_to_zshrc() {
@@ -23,9 +23,9 @@ append_to_zshrc() {
 
   if ! grep -Fqs "$text" "$zshrc"; then
     if [ "$skip_new_line" -eq 1 ]; then
-      printf "%s\n" "$text" >> "$zshrc"
+      printf "%s\\n" "$text" >> "$zshrc"
     else
-      printf "\n%s\n" "$text" >> "$zshrc"
+      printf "\\n%s\\n" "$text" >> "$zshrc"
     fi
   fi
 }
@@ -60,7 +60,7 @@ fi
 
 update_shell() {
   local shell_path;
-  shell_path="$(which zsh)"
+  shell_path="$(command -v zsh)"
 
   fancy_echo "Changing your shell to zsh ..."
   if ! grep "$shell_path" /etc/shells > /dev/null 2>&1 ; then
@@ -72,7 +72,7 @@ update_shell() {
 
 case "$SHELL" in
   */zsh)
-    if [ "$(which zsh)" != '/usr/local/bin/zsh' ] ; then
+    if [ "$(command -v zsh)" != '/usr/local/bin/zsh' ] ; then
       update_shell
     fi
     ;;