index-pack: Refactor base arguments of resolve_delta into a struct
We need to discard base objects which are not recently used if our
memory gets low, such as when we are unpacking a long delta chain
of a very large object.
To support tracking the available base objects we combine the
pointer and size into a struct. Future changes would allow the
data pointer to be free'd and marked NULL if memory gets low.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>