Function test 

pub fn test(refs: &[PushRef]) -> Outcome

pre-push. Mirrors run-tests-js: the range that is actually being pushed decides whether the suite runs, so a docs-only push costs nothing.

PER REF, not once for the whole push: git push origin a b carries two tips, and a single worktree checked out to the first one would run the second ref’s tests against the first ref’s tree — a real failure in the untested branch reported as a pass because nothing actually ran against it. Each ref that touches Rust gets its own worktree and its own verdict.