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From: Derrick Stolee <stolee@gmail.com>
To: Junio C Hamano <gitster@pobox.com>,
	Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, martin.agren@gmail.com,
	sandals@crustytoothpaste.net, me@ttaylorr.com,
	abhishekkumar8222@gmail.com,
	Derrick Stolee <derrickstolee@github.com>
Subject: Re: [PATCH 0/3] SHA-256: Update commit-graph and multi-pack-index formats
Date: Fri, 14 Aug 2020 16:34:56 -0400	[thread overview]
Message-ID: <04ebec72-07de-4494-688f-a9f48442906e@gmail.com> (raw)
In-Reply-To: <xmqqeeo9vxl0.fsf@gitster.c.googlers.com>

On 8/14/2020 3:25 PM, Junio C Hamano wrote:
> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> As discussed [1], there is some concern around binary file formats requiring
>> the context of the repository config in order to infer hash lengths. Two
>> formats that were designed with the hash transition in mind (commit-graph
>> and multi-pack-index) have bytes available to indicate the hash algorithm
>> used. Let's actually update these formats to be more self-contained with the
>> two hash algorithms being available.
>> ...
>> If this is the way we want to go with the formats, then I'll assist
>> coordinating these textual and semantic merge conflicts.
> 
> I agree that the files should be self-identifying, but have these
> changes tested without sha256 hash?

All of the test scripts pass with and without GIT_TEST_DEFAULT_HASH=sha256,
and this test in t5318 (and a similar one in t5319) are explicit about
testing both options:

+test_expect_success 'warn on improper hash version' '
+	git init --object-format=sha1 sha1 &&
+	(
+		cd sha1 &&
+		test_commit 1 &&
+		git commit-graph write --reachable &&
+		mv .git/objects/info/commit-graph ../cg-sha1
+	) &&
+	git init --object-format=sha256 sha256 &&
+	(
+		cd sha256 &&
+		test_commit 1 &&
+		git commit-graph write --reachable &&
+		mv .git/objects/info/commit-graph ../cg-sha256
+	) &&
+	(
+		cd sha1 &&
+		mv ../cg-sha256 .git/objects/info/commit-graph &&
+		git log -1 2>err &&
+		test_i18ngrep "commit-graph hash version 2 does not match version 1" err
+	) &&
+	(
+		cd sha256 &&
+		mv ../cg-sha1 .git/objects/info/commit-graph &&
+		git log -1 2>err &&
+		test_i18ngrep "commit-graph hash version 1 does not match version 2" err
+	)
+'
+

Since this tests exactly that the "hash version" byte is the same in
a SHA-1 repo, this checks that the new version of Git writes backwards-
compatible data in SHA-1 repos.

Or are you hinting at a more subtle test scenario that I missed?

Thanks,
-Stolee

  reply	other threads:[~2020-08-14 20:35 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-14 18:07 Derrick Stolee via GitGitGadget
2020-08-14 18:07 ` [PATCH 1/3] t/README: document GIT_TEST_DEFAULT_HASH Derrick Stolee via GitGitGadget
2020-08-14 19:02   ` Junio C Hamano
2020-08-14 20:39   ` Eric Sunshine
2020-08-14 20:41     ` Derrick Stolee
2020-08-14 18:07 ` [PATCH 2/3] commit-graph: use the hash version byte Derrick Stolee via GitGitGadget
2020-08-14 19:05   ` Junio C Hamano
2020-08-14 20:05     ` Taylor Blau
2020-08-14 20:11   ` brian m. carlson
2020-08-14 20:22     ` Junio C Hamano
2020-08-14 20:36     ` Derrick Stolee
2020-08-15 13:46       ` Martin Ågren
2020-08-14 18:07 ` [PATCH 3/3] multi-pack-index: use " Derrick Stolee via GitGitGadget
2020-08-14 20:14   ` brian m. carlson
2020-08-14 19:25 ` [PATCH 0/3] SHA-256: Update commit-graph and multi-pack-index formats Junio C Hamano
2020-08-14 20:34   ` Derrick Stolee [this message]
2020-08-14 21:41     ` Junio C Hamano
2020-08-17 14:04 ` [PATCH v2 " Derrick Stolee via GitGitGadget
2020-08-17 14:04   ` [PATCH v2 1/3] t/README: document GIT_TEST_DEFAULT_HASH Derrick Stolee via GitGitGadget
2020-08-17 14:04   ` [PATCH v2 2/3] commit-graph: use the "hash version" byte Derrick Stolee via GitGitGadget
2020-08-17 14:04   ` [PATCH v2 3/3] multi-pack-index: use hash version byte Derrick Stolee via GitGitGadget
2020-08-17 23:12   ` [PATCH v2 0/3] SHA-256: Update commit-graph and multi-pack-index formats brian m. carlson

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