Comment by steveklabnik

> If you have 10 commits for frontend and 10 for backend

In this model, you tend to want to amend, rather than add more commits. And so:

> they might start with 5 for backend, then 5 commits to each branch to iron out the interface and communication,

You don't add more commits here, you modify the commits in your stack instead.

> Now I need to rebase my frontend branch to sit on B6?

Yes, when you change something lower in the stack, the things on top need to be rebased. Because your forge understands that they're stacked, it can do this for you. And if there's conflicts, let you know that you need to resolve them, of course.

But in general, because you are amending the commits in the stack rather than adding to it, you don't need to move anything around.

> And wouldn't this separation normally be obvious e.g. by paths?

In the simplest case, sure. But for more complex work, that might not be the case. Furthermore, you said you have five commits for each; within those sets of five, this separation won't exist.