builtin/clone: initialize hash algorithm properly

builtin/clone: initialize hash algorithm properly

When performing a clone, we don't know what hash algorithm the other end
will support.  Currently, we don't support fetching data belonging to a
different algorithm, so we must know what algorithm the remote side is
using in order to properly initialize the repository.  We can know that
only after fetching the refs, so if the remote side has any references,
use that information to reinitialize the repository with the correct
hash algorithm information.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>