Each "struct ref" has a boolean flag that is set by the
fetch code to determine whether the ref should be marked as
"not-for-merge" or not when we write it out to FETCH_HEAD.
It would be useful to turn this boolean into a tri-state,
with the third state meaning "do not bother writing it out
to FETCH_HEAD at all". That would let us add extra refs to
the set of refs to be stored (e.g., to store copies of
things we fetched) without impacting FETCH_HEAD.
This patch turns it into an enum that covers the tri-state
case, and hopefully makes the code more explicit and easier
to read.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>