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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: Git List <git@vger.kernel.org>,
	Jonathan Tan <jonathantanmy@google.com>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH 00/24] SHA-256 test fixes, part 8
Date: Mon, 13 Jan 2020 23:17:05 +0000
Message-ID: <20200113231705.GU6570@camp.crustytoothpaste.net> (raw)
In-Reply-To: <CAPig+cReDPs8D1L3+Z4sMn__JuU-Ezs+fOSF00=_tNxa0DotFQ@mail.gmail.com>

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On 2020-01-13 at 13:41:44, Eric Sunshine wrote:
> On Mon, Jan 13, 2020 at 7:40 AM brian m. carlson
> <sandals@crustytoothpaste.net> wrote:
> > I suspect that t3404 also has a bug, since the object IDs that are
> > supposed to collide do not, according to my instrumentation of the test.
> > I'm unsure what the intended collision was and consequently haven't
> > fixed it.  However, it does work with SHA-256 as it stands and is no
> > more or less functional than with SHA-1, so I've removed the
> > prerequisite.
> 
> The test itself is fine, but it is one of those unfortunate cases of
> checking for absence of something (which is a wide net). As explained
> by the commit message[1] of the patch which added the test, the
> collision occurred only between short OID's. The patch[2] which fixed
> the problem did so by avoiding short OID's in the scripted
> implementation of `git rebase -i` (and also flipped the test from
> `text_expect_failure` to `test_expect_success`).
> 
> The test, as currently implemented, is very much specific to SHA-1
> since the FAKE_COMMIT_MESSAGE="collide2 ac4f2ee" it uses only produces
> a collision with short OID's when SHA-1 is the hashing function, so
> the prerequisite is correct and serves as documentation (even if it
> doesn't affect the outcome of the test). Removing that prerequisite
> should only be done if the test is updated with a different
> FAKE_COMMIT_MESSAGE which causes a short OID collision when SHA-256 is
> used.

I'll take another look.  When I looked at the output, it looked like
they didn't collide anymore even under SHA-1, but perhaps I instrumented
the test wrong and therefore got the wrong result.  Thanks for double
checking.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 12:38 brian m. carlson
2020-01-13 12:38 ` [PATCH 01/24] t/lib-pack: support SHA-256 brian m. carlson
2020-01-13 12:38 ` [PATCH 02/24] t3206: make hash size independent brian m. carlson
2020-01-13 12:38 ` [PATCH 03/24] t3305: annotate with SHA1 prerequisite brian m. carlson
2020-01-13 12:38 ` [PATCH 04/24] t3308: make test work with SHA-256 brian m. carlson
2020-01-13 12:38 ` [PATCH 05/24] t3309: " brian m. carlson
2020-01-13 12:38 ` [PATCH 06/24] t3310: " brian m. carlson
2020-01-13 12:38 ` [PATCH 07/24] t3311: " brian m. carlson
2020-01-13 12:38 ` [PATCH 08/24] t3404: remove SHA1 prerequisite brian m. carlson
2020-01-13 12:38 ` [PATCH 09/24] t4013: make test hash independent brian m. carlson
2020-01-13 12:38 ` [PATCH 10/24] t4060: make test work with SHA-256 brian m. carlson
2020-01-13 12:38 ` [PATCH 11/24] t4211: make test hash independent brian m. carlson
2020-01-13 12:38 ` [PATCH 12/24] t5302: make hash size independent brian m. carlson
2020-01-13 12:38 ` [PATCH 13/24] t5309: make test hash independent brian m. carlson
2020-01-13 12:38 ` [PATCH 14/24] t5313: " brian m. carlson
2020-01-13 12:38 ` [PATCH 15/24] t5321: " brian m. carlson
2020-01-13 12:38 ` [PATCH 16/24] t5515: " brian m. carlson
2020-01-13 12:38 ` [PATCH 17/24] t5318: update for SHA-256 brian m. carlson
2020-01-13 13:50   ` Eric Sunshine
2020-01-13 23:14     ` brian m. carlson
2020-01-13 12:38 ` [PATCH 18/24] t5616: use correct filter syntax brian m. carlson
2020-01-13 20:28   ` [PATCH] t5616: make robust to delta base change Jonathan Tan
2020-01-13 23:11     ` brian m. carlson
2020-01-25 22:43     ` brian m. carlson
2020-01-13 12:38 ` [PATCH 19/24] t5607: make hash size independent brian m. carlson
2020-01-13 12:38 ` [PATCH 20/24] t5703: make test work with SHA-256 brian m. carlson
2020-01-13 13:53   ` Eric Sunshine
2020-01-13 23:15     ` brian m. carlson
2020-01-13 12:38 ` [PATCH 21/24] t5703: switch tests to use test_oid brian m. carlson
2020-01-13 12:38 ` [PATCH 22/24] t6000: abstract away SHA-1-specific constants brian m. carlson
2020-01-13 12:38 ` [PATCH 23/24] t6006: make hash size independent brian m. carlson
2020-01-13 12:38 ` [PATCH 24/24] t6024: update for SHA-256 brian m. carlson
2020-01-13 13:41 ` [PATCH 00/24] SHA-256 test fixes, part 8 Eric Sunshine
2020-01-13 23:17   ` brian m. carlson [this message]
2020-01-13 23:34     ` Eric Sunshine
2020-01-16  0:28 ` Johannes Schindelin

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