Convert the name member of struct merge_remote_desc to a FLEX_ARRAY and
use FLEX_ALLOC_STR to build the struct. This halves the number of
memory allocations, saves the storage for a pointer and avoids an
indirection when reading the name.
Suggested-by: Jeff King <peff@peff.net> 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>