Jeff King <> writes:

> On Wed, Aug 01, 2012 at 03:10:55PM -0700, Junio C Hamano wrote:
> ...
>> When you move porn/0001.jpg in the preimage to naughty/00001.jpg in
>> the postimage, they both can hit "*.jpg contentid=jpeg" line in the
>> top-level .gitattribute file, and the contentid driver for jpeg type
>> may strip exif and hash the remainder bits in the image to come up
>> with a token you can use in a similar way as object ID is used in
>> the exact rename detection phase.
>> Just thinking aloud.
> Ah, I see. That still feels like way too specific a use case to me. A
> much more general use case to me would be a contentid driver which
> splits the file into multiple chunks (which can be concatenated to
> arrive at the original content), and marks chunks as "OK to delta" or
> "not able to delta".  In other words, a content-specific version of the
> bup-style splitting that people have proposed.
> Assuming we split a jpeg into its EXIF bits (+delta) and its image bits
> (-delta), then you could do a fast rename or pack-objects comparison
> between two such files (in fact, with chunked object storage,
> pack-objects can avoid looking at the image parts at all).
> However, it may be the case that such "smart" splitting is not
> necessary, as stupid and generic bup-style splitting may be enough. I
> really need to start playing with the patches you wrote last year that
> started in that direction.

I wasn't interested in "packing split object representation",
actually.  The idea was still within the context of "rename".

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