Re: [PATCH/RFC] index-pack: produce pack index version 3

> On Wed, Aug 15, 2012 at 10:42 PM, Junio C Hamano <gitster@pobox.com> wrote:
> ...
>> An obvious way to record the "delta chain" is to simply keep the
>> name_hash of each object in the pack, which would need 2 bytes per
>> object in the pack, that would bloat pack_idx_entry size from 32
>> bytes to 34 bytes per entry.  That way, after your bitmap discovers
>> an object that cannot reuse existing deltas, you can throw it, other
>> such objects with the same name-hash, and then objects that you know
>> will be available to the recipient (you mark the last category of
>> objects as "preferred base"), into the delta_list so that they are
>> close together in the delta window.
>
> Yes, this is one thought I had. Inside of JGit I think the name hash
> is 32 bits, not 16 bits. Storing the name hash into the *.idx file
> means we need to codify what the name hash algorithm is for a given
> *.idx file version, and compatible implementations of Git must use the
> same hash function. Thus far the name hash has been an in-memory
> transient concept that doesn't need to be persisted across runs of the
> packer. Storing it means we have to do that.