merge-recursive: fix verbose output for multiple base trees

merge-recursive: fix verbose output for multiple base trees

One of the indirect callers of make_virtual_commit() passes the result of
oid_to_hex() as the name, i.e. a pointer to a static buffer.  Since the
function uses that string pointer directly in building a struct
merge_remote_desc, multiple entries can end up sharing the same name
inadvertently.

Fix that by calling set_merge_remote_desc(), which creates a copy of the
string, instead of building the struct by hand.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>