Heya, what do I do with this?

gt sync   
🌲 Pulling main from remote...
main is up to date.
🧹 Checking if any branches have been merged/closed and can be deleted...
feature/rb-2373-optimize-updatebatch does not need to be restacked on main.
ESClient_to_use_futures does not need to be restacked on main.

The following branches could not be restacked cleanly:
▸ 09-21-ESClient_Internal_now_uses_futures
You can resolve conflicts with gt restack.

I don't actually need anything from this branch, but I want to resolve the error. What are my options?

You can checkout

09-21-ESClient_Internal_now_uses_futures

and run

gt restack

and resolve conflicts.

OK, thanks, that makes more sense.