Re: [PATCH 2/5] sha1_file: fix hardcoded size in null_sha1

> Junio C Hamano <gitster@pobox.com> wrote:
>
>> I said this is OK for "null" because we assume we will use ^\0{len}$
>> for any hash function we choose as the "impossible" value, and for
>> that particular use pattern, we do not need such a union.  Just
>> letting the caller peek at an appropriate number of bytes at the
>> beginning of that NUL buffer for hash the caller wants to use is
>> sufficient.
>
> Do you think I should record this explanation as either commit message
> or comment in sha1_file.c?
>
>> MAX is inevitable only if we envision that we have to handle objects
>> named using two or more hashing schemes at the same time, with the
>> same binary and during the same run inside a single process.
>
> I think this will be the case if "transition one local repository at
> a time" from Jonathan Nieder's transition plan will be followed.
> This plan assumes object_id translation happening e.g. during fetch
> operation.