Seperate repo for trellis and bedrock?

I’ve been using trellis and bedrock on separate git repos
how should I set the repo_subtree_path option in wordpress_sites? just …/site or something else? should they be in the same repo?

my structure is like this
trellis # wp-server.git
site # bedrock-site.git

You can just delete the repo_subtree_path. They don’t need to be in the same repo. Trellis just uses the repo to install the Bedrock site. Trellis doesn’t need to be version controlled itself — it’s still a good idea though.

so what should I put in repo

Bedrock, which it sounds like you are already doing.