Add tests that for-each-ref correctly reports broken loose reference
files and references that point at missing objects. In fact, two of
these tests fail, because (1) NULL_SHA1 is not recognized as an
invalid reference value, and (2) for-each-ref doesn't respect
REF_ISBROKEN. Fixes to come.
Note that when for-each-ref is run with a --format option that doesn't
require the object to be looked up, then we should still notice if a
loose reference file is corrupt or contains NULL_SHA1, but we don't
notice if it points at a missing object because we don't do an object
lookup. This is OK.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
