index-pack: eliminate unlimited recursion in get_base_data()

index-pack: eliminate unlimited recursion in get_base_data()

Revese the order of delta applying so that by the time a delta is
applied, its base is either non-delta or already inflated.
get_base_data() is still recursive, but because base's data is always
ready, the inner get_base_data() call never has any chance to call
itself again.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>