Re: [PATCH] pack-objects: reuse data from existing pack.

Nicolas Pitre [off-list ref] writes:

On Wed, 15 Feb 2006, Junio C Hamano wrote:

quoted

    Generating pack...
    Done counting 12233 objects.
    Packing 12233 objects.....................
    60a88b3979df41e22d1edc3967095e897f720192
    Total 12233, written 12233, reused 12177
...

In fact, the resulting pack should be identical with or without this 
patch, shouldn't it?

Not necessarily.  The delta-depth limitation is currently lifted
when reusing deltified objects (finding out the current depth is
not so expensive compared to uncompress-delta-recompress cycle,
but still costs somewhat, and the objective of this exercise is
to gain performance).

Notice the numbers 'written' and 'reused' in the output?
The difference in that example comes from the fact that I am
omitting some objects from the set of objects to be packed
(v1.0.0 is ancient) in a repository where some newer objects are
packed.  Since packing-delta goes backwards, what is in v1.0.0
but not in my tip tends to be delitified in the original pack,
but the resulting pack needs to have them expanded -- that is
where the difference comes from.

A cleaned-up patch will be in "pu" branch tonight.  I considered
putting it in "next", but decided against it.  I have not spent
enough time really beating on it, although I haven't seen major
breakage.