Function open_repo_view_at 

pub fn open_repo_view_at(
    view: &str,
    mode_id: &str,
    store: &BufferStoreHandle,
    scopes: &RepoScopes,
    active: BufferId,
    at: Option<&Path>,
) -> Effect

PC.3: open_repo_view for a repository named EXPLICITLY.

The form magit-repo-scoping.md deferred rather than rejected — “Rejected as the primary mechanism … Worth having later as an explicit form.” The implicit resolution in that document’s §2 is untouched: at = None is open_repo_view exactly, and an argument-less :magit-status still resolves from the buffer.

This is complementary, not a replacement, and the distinction is the whole reason the original rejection stands: making the COMMON case (working across two checkouts) the one that needs an argument would be backwards. What needs an argument is the uncommon case — a project chosen from a picker, where the caller already knows which repository it means.