Re: [PATCH v2] pack-format.txt: more details on pack file format

>> +=== Deltified representation
>> +
>> +Conceptually there are only four object types: commit, tree, tag and
>> +blob. However to save space, an object could be stored as a "delta" of
>> +another "base" object. These representations are assigned new types
>> +ofs-delta and ref-delta, which is only valid in a pack file.
>
> ...only valid...
>
> as opposed to loose objects or as opposed to referencing cross-packs?
> I would think the former, not the latter.

>> +Both ofs-delta and ref-delta store the "delta" against another
>> +object. The difference between them is, ref-delta directly encodes
>> +20-byte base object name. If the base object is in the same pack,
>> +ofs-delta encodes the offset of the base object in the pack instead.
>
> Reading this paragraph clears up the question from before.
> The ref delta is a delta to another "reference by hash id (sha1)".
> What abbreviation is OFS? OFfSet ?

>> +The delta data is a sequence of instructions to reconstruct an object
>> +from the base object.
>
> As said before the base object is of type 1..4, we do not "delta-on-delta"
> yet, but to construct the object we have to create the base object first,
> which itself can be represented as a deltified object leading to a delta
> chain.