connect: annotate refs with their symref information in get_remote_head()

connect: annotate refs with their symref information in get_remote_head()

By doing this, clients of upload-pack can now reliably tell what ref
a symbolic ref points at; the updated test in t5505 used to expect
failure due to the ambiguity and made sure we give diagnostics, but
we no longer need to be so pessimistic. Make sure we correctly learn
which branch HEAD points at from the other side instead.

Signed-off-by: Junio C Hamano <gitster@pobox.com>