repack: turn on "ref paranoia" when doing a destructive repack
If we are repacking with "-ad", we will drop any unreachable
objects. Likewise, using "-Ad --unpack-unreachable=<time>"
will drop any old, unreachable objects. In these cases, we
want to make sure the reachability we compute with "--all"
is complete. We can do this by passing GIT_REF_PARANOIA=1 in
the environment to pack-objects.
Note that "-Ad" is safe already, because it only loosens
unreachable objects. It is up to "git prune" to avoid
deleting them.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>