Similar to the recursion in packed_object_info(), this leads to
problems on stack-space-constrained systems in the presence of long
delta chains.
We proceed in three phases:
1. Dig through the delta chain, saving each delta object's offsets and
size on an ad-hoc stack.
2. Unpack the base object at the bottom.
3. Unpack and apply the deltas from the stack.
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>