Of course, you shouldn't start a project from 10 repos. But the downside is while you live in a single repo all the tooling get tuned to work with a single repo

Of course, you shouldn't start a project from 10 repos. But the downside is while you live in a single repo all the tooling get tuned to work with a single repo. And then there is no way to go multi-repo when you need to. So advice would be: start small but think big :)