update: return git error code on failure (#9238)

Fixes #9237

tools/upgrade.sh

@@ -68,6 +68,7 @@ then
   printf "${BLUE}${BOLD}%s ${UNDER}%s${RESET}\n" "Want to get involved in the community? Join our Discord:" "https://discord.gg/ohmyzsh"
   printf "${BLUE}${BOLD}%s ${UNDER}%s${RESET}\n" "Get your Oh My Zsh swag at:" "https://shop.planetargon.com/collections/oh-my-zsh"
 else
+  status=$?
   printf "${RED}%s${RESET}\n" 'There was an error updating. Try again later?'
 fi
 
@@ -76,3 +77,6 @@ case "$resetAutoStash" in
   "") git config --unset rebase.autoStash ;;
   *) git config rebase.autoStash "$resetAutoStash" ;;
 esac
+
+# Exit with `1` if the update failed
+exit $status