Is there a way to specify which branch for codex cloud exec?

You can now send out commands to codex from your cli using (eg.):

codex cloud exec --env xxx…xxx --attempts 1 "do some cool additions…”

However, you can’t (or at least I can’t figure out how to) specify the branch that you want the work done on? What am I missing here, this feels like an obvious --branch cli arg that doesn’t exist?

I’m assuming I’ve just missed how to do this - has anyone else done it?