GitHub stacked PRs with gh stack

A stack is a chain of PRs, bottom to top, registered with GitHub through the gh stack CLI extension.

Key invariant

A chain of PR base branches is not automatically a GitHub Stack. The stack must be registered through gh stack submit (or the stack API). Verify with:

gh stack view --short
gh stack view --json

The output must show a Stack #<number>. Correct PR base branches alone are insufficient proof.

Stack trunk

The stack trunk is the base of the bottom PR. GitHub evaluates every PR in the stack against it, so initialize, rebase and simulate merges against the stack trunk, fetched fresh from the remote.