refs: fix ref storage format for submodule ref stores

When opening a submodule ref storage we accidentally use the ref storage
format of the owning repository, not of the submodule repository. As
submodules may have a different storage format than their parent repo
this can lead to bugs when trying to access the submodule ref storage
from the parent repository.

One such bug was reported when performing a recursive pull with mixed
ref stores, which fails with:

    $ git pull --recursive
    fatal: Unable to find current revision in submodule path 'path/to/sub'

The same issue occurs when adding a repository contained in the working
tree with a different ref storage format via `git submodule add`.

Fix the bug by using the submodule repository's ref storage format
instead and add some tests. Note that the test for `git submodule
status` was included as a precaution, only. The command worked alright
even without the bugfix.

Reported-by: Jeppe Øland <[email protected]>
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

refs.c

@@ -2011,7 +2011,7 @@ struct ref_store *repo_get_submodule_ref_store(struct repository *repo,
 		free(subrepo);
 		goto done;
 	}
-	refs = ref_store_init(subrepo, the_repository->ref_storage_format,
+	refs = ref_store_init(subrepo, subrepo->ref_storage_format,
 			      submodule_sb.buf,
 			      REF_STORE_READ | REF_STORE_ODB);
 	register_ref_store_map(&repo->submodule_ref_stores, "submodule",

t/t7424-submodule-mixed-ref-formats.sh

@@ -18,7 +18,23 @@ do
 	fi
 
 test_expect_success 'setup' '
-	git config set --global protocol.file.allow always
+	git config set --global protocol.file.allow always &&
+	# Some tests migrate the ref storage format, which does not work with
+	# reflogs at the time of writing these tests.
+	git config set --global core.logAllRefUpdates false
+'
+
+test_expect_success 'add existing repository with different ref storage format' '
+	test_when_finished "rm -rf parent" &&
+
+	git init parent &&
+	(
+		cd parent &&
+		test_commit parent &&
+		git init --ref-format=$OTHER_FORMAT submodule &&
+		test_commit -C submodule submodule &&
+		git submodule add ./submodule
+	)
 '
 
 test_expect_success 'recursive clone propagates ref storage format' '
@@ -59,6 +75,58 @@ test_expect_success 'clone submodules with different ref storage format' '
 	test_ref_format downstream/submodule "$OTHER_FORMAT"
 '
 
+test_expect_success 'status with mixed submodule ref storages' '
+	test_when_finished "rm -rf submodule main" &&
+
+	git init submodule &&
+	test_commit -C submodule submodule-initial &&
+	git init main &&
+	git -C main submodule add "file://$(pwd)/submodule" &&
+	git -C main commit -m "add submodule" &&
+	git -C main/submodule refs migrate --ref-format=$OTHER_FORMAT &&
+
+	# The main repository should use the default ref format now, whereas
+	# the submodule should use the other format.
+	test_ref_format main "$GIT_DEFAULT_REF_FORMAT" &&
+	test_ref_format main/submodule "$OTHER_FORMAT" &&
+
+	cat >expect <<-EOF &&
+	 $(git -C main/submodule rev-parse HEAD) submodule (submodule-initial)
+	EOF
+	git -C main submodule status >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'recursive pull with mixed formats' '
+	test_when_finished "rm -rf submodule upstream downstream" &&
+
+	# Set up the initial structure with an upstream repository that has a
+	# submodule, as well as a downstream clone of the upstream repository.
+	git init submodule &&
+	test_commit -C submodule submodule-initial &&
+	git init upstream &&
+	git -C upstream submodule add "file://$(pwd)/submodule" &&
+	git -C upstream commit -m "upstream submodule" &&
+
+	# Clone the upstream repository such that the main repo and its
+	# submodules have different formats.
+	git clone --no-recurse-submodules "file://$(pwd)/upstream" downstream &&
+	git -C downstream submodule update --init --ref-format=$OTHER_FORMAT &&
+	test_ref_format downstream "$GIT_DEFAULT_REF_FORMAT" &&
+	test_ref_format downstream/submodule "$OTHER_FORMAT" &&
+
+	# Update the upstream submodule as well as the owning repository such
+	# that we can do a recursive pull.
+	test_commit -C submodule submodule-update &&
+	git -C upstream/submodule pull &&
+	git -C upstream commit -am "update the submodule" &&
+
+	git -C downstream pull --recurse-submodules &&
+	git -C upstream/submodule rev-parse HEAD >expect &&
+	git -C downstream/submodule rev-parse HEAD >actual &&
+	test_cmp expect actual
+'
+
 done
 
 test_done