The "nonfastforward" and "update" fields are only used while
deciding what value to assign to the "status" locally in a single
function. Remove them from the "struct ref".
The "requires_force" field is not used to decide if the proposed
update requires a --force option to succeed, or to record such a
decision made elsewhere. It is used by status reporting code that
the particular update was "forced". Rename it to "forced_update",
and move the code to assign to it around to further clarify how it
is used and what it is used for.