Subject: Re: [PATCH 2/2] git-format-patch: Document format for binary patch

From: Junio C Hamano <[email-masked]>
Date: Thu, 25 Mar 2021 11:25:48 -0700

Bagas Sanjaya <[email-masked]> writes:

> On 25/03/21 00.53, Junio C Hamano wrote:
>> I do not think this is all that useful; it clutters the description
>> for a reader who is not interested in reimplementing an encoder or a
>> decoder from the document.
>> And it is way too insufficient for a reader who wants to reimplement
>> an encoder or a decoder.  For example,
>>   - It does not say anything about what the delta is and how it is
>>     computed.
>>   - The 'z' is redundant; the more important is to say that the
>> first
>>     byte signals how many bytes are on that line and it is a mere
>>     artifact that we cram up to 52 bytes on a line.
>>   - It does not say anything about how the binary patch ensures that
>>     it is reversible (i.e. can be given to "git apply -R").
>> Thanks.
>> 
> Hmmm...
>
> I write this patch from "naive" observation of git format-patch's
> behavior when given binary files in the commit.
>
> Perhaps someone which is more familiar in base85 {en,de}coder and binary
> patch in general can write better documentation than what I send here.

I do not mind reviewing an update to an existing document or a new
document in Documentation/technical/ somewhere, if somebody is
motivated enough to write the details to a degree that would allow
reimplementation of the encoder and the decoder.  I just do not think
it belongs to the end-user-facing document of "format-patch", whose
target is users of the "format-patch" command, not reimplementors of
the command.