From: Junio C Hamano <gitster@pobox.com>
To: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, johannes.schindelin@gmx.de, peff@peff.net,
ps@pks.im, me@ttaylorr.com, johncai86@gmail.com,
newren@gmail.com, Derrick Stolee <stolee@gmail.com>
Subject: Re: [PATCH 1/4] pack-objects: add --full-name-hash option
Date: Mon, 09 Sep 2024 10:45:51 -0700 [thread overview]
Message-ID: <xmqqed5ssots.fsf@gitster.g> (raw)
In-Reply-To: <ff30f774ca82662bb25291804559bf3f2de061c2.1725890211.git.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Mon, 09 Sep 2024 13:56:47 +0000")
"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.
Thanks.
next prev parent reply other threads:[~2024-09-09 17:45 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-09 13:56 [PATCH 0/4] pack-objects: create new name-hash algorithm Derrick Stolee via GitGitGadget
2024-09-09 13:56 ` [PATCH 1/4] pack-objects: add --full-name-hash option Derrick Stolee via GitGitGadget
2024-09-09 17:45 ` Junio C Hamano [this message]
2024-09-10 2:31 ` Derrick Stolee
2024-09-09 13:56 ` [PATCH 2/4] git-repack: update usage to match docs Derrick Stolee via GitGitGadget
2024-09-09 17:48 ` Junio C Hamano
2024-09-09 13:56 ` [PATCH 3/4] p5313: add size comparison test Derrick Stolee via GitGitGadget
2024-09-09 13:56 ` [PATCH 4/4] p5314: add a size test for name-hash collisions Derrick Stolee via GitGitGadget
2024-09-09 16:07 ` [PATCH 0/4] pack-objects: create new name-hash algorithm Derrick Stolee
2024-09-09 18:06 ` Junio C Hamano
2024-09-10 2:37 ` Derrick Stolee
2024-09-10 14:56 ` Taylor Blau
2024-09-10 21:05 ` Derrick Stolee
2024-09-11 6:32 ` Jeff King
2024-09-10 16:07 ` Junio C Hamano
2024-09-10 20:36 ` Junio C Hamano
2024-09-10 21:09 ` Derrick Stolee
2024-09-18 20:46 ` [PATCH v2 0/6] " Derrick Stolee via GitGitGadget
2024-09-18 20:46 ` [PATCH v2 1/6] pack-objects: add --full-name-hash option Derrick Stolee via GitGitGadget
2024-09-19 21:56 ` Junio C Hamano
2024-09-18 20:46 ` [PATCH v2 2/6] repack: test " Derrick Stolee via GitGitGadget
2024-09-19 22:11 ` Junio C Hamano
2024-09-18 20:46 ` [PATCH v2 3/6] pack-objects: add GIT_TEST_FULL_NAME_HASH Derrick Stolee via GitGitGadget
2024-09-19 22:22 ` Junio C Hamano
2024-09-23 1:39 ` Derrick Stolee
2024-09-18 20:46 ` [PATCH v2 4/6] git-repack: update usage to match docs Derrick Stolee via GitGitGadget
2024-09-18 20:46 ` [PATCH v2 5/6] p5313: add size comparison test Derrick Stolee via GitGitGadget
2024-09-19 21:58 ` Junio C Hamano
2024-09-23 1:50 ` Derrick Stolee
2024-09-23 16:14 ` Junio C Hamano
2024-09-18 20:46 ` [PATCH v2 6/6] test-tool: add helper for name-hash values Derrick Stolee via GitGitGadget
2024-09-24 7:02 ` Patrick Steinhardt
2024-09-25 13:35 ` Derrick Stolee
2024-09-18 23:30 ` [PATCH v2 0/6] pack-objects: create new name-hash algorithm Derrick Stolee
2024-10-04 21:17 ` Junio C Hamano
2024-10-04 22:30 ` Taylor Blau
2024-10-04 22:35 ` Jeff King
2024-10-08 18:32 ` Derrick Stolee
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