match_refs() returns non-zero if there is an error in
match_explicit_refs(), without handling any remaining pattern ref specs.
Its existing callers exit upon receiving non-zero, so a partial result
is of no consequence to them; however a new caller, builtin-remote, is
interested in the complete result even if there are errors in
match_explicit_refs().
Signed-off-by: Jay Soffian <jaysoffian@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>