diff mbox series

[2/2] bundle: default to SHA1 when reading bundle headers

Message ID 7e15c3daf95283f62030fe7b5dd0bbf8e467881a.1723540604.git.ps@pks.im (mailing list archive)
State Accepted
Commit 96a9a3e42e85874ba5edfcf86d91f7d8c05d5f94
Headers show
Series bundle: fix handling of object format | expand

Commit Message

Patrick Steinhardt Aug. 13, 2024, 9:18 a.m. UTC
We hit a segfault when trying to open a bundle via `git bundle
list-heads` when running outside of a repository. This is caused by
c8aed5e8da (repository: stop setting SHA1 as the default object hash,
2024-05-07), which stopped setting the default object hash so that
`the_hash_algo` is a `NULL` pointer when running outside of any repo.

This is only a symptom of a deeper issue though. Bundles default to the
SHA1 object format unless they advertise an "@object-format=" header.
Consequently, it has been wrong in the first place to use the object
format used by the current repository when parsing bundles. The
consequence is that trying to open a bundle that uses a different object
hash than the current repository will fail:

    $ git bundle list-heads sha1.bundle
    error: unrecognized header: ee4b540943284700a32591ad09f7e15bdeb2a10c HEAD (45)

Fix the bug by defaulting to the SHA1 object hash. We already handle the
"@object-format=" header as expected, so we don't need to adapt this
part.

Helped-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 bundle.c               |  7 ++++++-
 t/t6020-bundle-misc.sh | 25 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

Comments

Jeff King Aug. 13, 2024, 11:24 a.m. UTC | #1
On Tue, Aug 13, 2024 at 11:18:15AM +0200, Patrick Steinhardt wrote:

> This is only a symptom of a deeper issue though. Bundles default to the
> SHA1 object format unless they advertise an "@object-format=" header.
> Consequently, it has been wrong in the first place to use the object
> format used by the current repository when parsing bundles. The
> consequence is that trying to open a bundle that uses a different object
> hash than the current repository will fail:
> 
>     $ git bundle list-heads sha1.bundle
>     error: unrecognized header: ee4b540943284700a32591ad09f7e15bdeb2a10c HEAD (45)

That makes sense. And your test below, which covers a mismatch in the
hash of the bundle vs the containing repo, would have failed even before
the segfault issue. Nice.

> Fix the bug by defaulting to the SHA1 object hash. We already handle the
> "@object-format=" header as expected, so we don't need to adapt this
> part.

Yeah, this fix turned out to be delightfully simple as a result.

Both this patch and the first one look good to me. Thanks for jumping on
this.

-Peff
Junio C Hamano Aug. 13, 2024, 3:11 p.m. UTC | #2
Jeff King <peff@peff.net> writes:

> Yeah, this fix turned out to be delightfully simple as a result.
>
> Both this patch and the first one look good to me. Thanks for jumping on
> this.

They look good to me too.  Thanks, all.
diff mbox series

Patch

diff --git a/bundle.c b/bundle.c
index ce164c37bc..b0a8a925cb 100644
--- a/bundle.c
+++ b/bundle.c
@@ -89,7 +89,12 @@  int read_bundle_header_fd(int fd, struct bundle_header *header,
 		goto abort;
 	}
 
-	header->hash_algo = the_hash_algo;
+	/*
+	 * The default hash format for bundles is SHA1, unless told otherwise
+	 * by an "object-format=" capability, which is being handled in
+	 * `parse_capability()`.
+	 */
+	header->hash_algo = &hash_algos[GIT_HASH_SHA1];
 
 	/* The bundle header ends with an empty line */
 	while (!strbuf_getwholeline_fd(&buf, fd, '\n') &&
diff --git a/t/t6020-bundle-misc.sh b/t/t6020-bundle-misc.sh
index 703434b472..34b5cd62c2 100755
--- a/t/t6020-bundle-misc.sh
+++ b/t/t6020-bundle-misc.sh
@@ -659,4 +659,29 @@  test_expect_success 'unbundle outside of a repository' '
 	test_cmp expect err
 '
 
+test_expect_success 'list-heads outside of a repository' '
+	git bundle create some.bundle HEAD &&
+	cat >expect <<-EOF &&
+	$(git rev-parse HEAD) HEAD
+	EOF
+	nongit git bundle list-heads "$(pwd)/some.bundle" >actual &&
+	test_cmp expect actual
+'
+
+for hash in sha1 sha256
+do
+	test_expect_success "list-heads with bundle using $hash" '
+		test_when_finished "rm -rf hash" &&
+		git init --object-format=$hash hash &&
+		test_commit -C hash initial &&
+		git -C hash bundle create hash.bundle HEAD &&
+
+		cat >expect <<-EOF &&
+		$(git -C hash rev-parse HEAD) HEAD
+		EOF
+		git bundle list-heads hash/hash.bundle >actual &&
+		test_cmp expect actual
+	'
+done
+
 test_done