From: Derrick Stolee <stolee@gmail.com>
Date: Tue, 10 Sep 2024 02:31:36 GMT
Subject: Re: [PATCH 1/4] pack-objects: add --full-name-hash option
Message-ID: <7d7b9c30-c95a-4dcd-a5d7-1fca5ddb99e7@gmail.com>
In-Reply-To: <xmqqed5ssots.fsf@gitster.g>

On 9/9/24 1:45 PM, Junio C Hamano wrote:
> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> This is not meant to be cryptographic at all, but uniformly distributed
>> across the possible hash values. This creates a hash that appears
>> pseudorandom. There is no ability to consider similar file types as
>> being close to each other.
> 
> Another consideration we had when designing the current mechanism,
> which is more important than "compare .c files with each other", is
> to handle the case where a file is moved across directory boundary
> without changing its name.  These "hash collissions" are meant to be
> a part of obtaining _good_ paring of blobs that ought to be similar
> to each other.  In other words, we wanted them to collide so that we
> do not have to be negatively affected by moves.
> 
> I am not saying that we should not update the pack name hash; I am
> just saying that "consider similar file types" as if that is the
> most important aspect of the current hash, is misleading.

Thank you for this extra aspect, which has clarified some of my
thinking and I will use in future versions.

Thanks,
-Stolee