read_info_alternates is not used from outside, so let's make it static.
We have to declare the function before link_alt_odb_entry instead of
moving the code around, link_alt_odb_entry calls read_info_alternates,
which in turn calls link_alt_odb_entry.
Signed-off-by: Stefan Beller <sbeller@google.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>