This variable is only ever used by the routines in pager.c,
and other parts of the code should always use those routines
(like git_pager()) to make decisions about which pager to
use. Let's reduce its scope to prevent accidents.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>