Re: [PATCH 3/4] diff: introduce diff.<driver>.binary

[Matthieu Moy <Matthieu.Moy@imag.fr>]

Junio C Hamano <gitster@pobox.com> writes:

> The textconv filter is primarily for humans to be able to view the diff,
> as far as I understand it, but what would this facility do to the patch
> exchange workflow?  There needs either one or both of the following:
>
>  - A command line option to Porcelains to override textconv so that an
>    applicable binary diff can be obtained upon request (or format-patch
>    always disables textconv); and/or

To me (and others in this thread AIUI), the textconv should only
replace the (frustrating) "binary files differ" in porcelain.

>  - You teach git-apply to use a reverse transformation of textconv, so
>    that it does, upon reception of a textconv diff:
>
>    (1) pass existing preimage through textconv;
>    (2) apply the patch;
>    (3) convert the result back to binary.

I can imagine corner-case scenarios where this would be applicable and
somehow usefull (like: modifying _only_ the EXIF tags on one end, and
expect to be able to view and apply the tags modification on the other
end), but I don't think that's something important to worry about. As
other said, it would be really hard to set up for users, with little
benefits.

One possibility that would be simpler to set up would be to include
both the binary diff and the textconved diff in format-patch, and have
"git apply" just verify that the textconv actually matches the binary
diff after applying it. But that reduces the security issue without
really solving it: one could very well send a binary patch that
changes both the image and the exiftags, and claim it only changes the
tags.

In short: agreed with Peff ;-).

-- 
Matthieu