Sync with 2.39.4

* maint-2.39: (38 commits)
  Git 2.39.4
  fsck: warn about symlink pointing inside a gitdir
  core.hooksPath: add some protection while cloning
  init.templateDir: consider this config setting protected
  clone: prevent hooks from running during a clone
  Add a helper function to compare file contents
  init: refactor the template directory discovery into its own function
  find_hook(): refactor the `STRIP_EXTENSION` logic
  clone: when symbolic links collide with directories, keep the latter
  entry: report more colliding paths
  t5510: verify that D/F confusion cannot lead to an RCE
  submodule: require the submodule path to contain directories only
  clone_submodule: avoid using `access()` on directories
  submodules: submodule paths must not contain symlinks
  clone: prevent clashing git dirs when cloning submodule in parallel
  t7423: add tests for symlinked submodule directories
  has_dir_name(): do not get confused by characters < '/'
  docs: document security issues around untrusted .git dirs
  upload-pack: disable lazy-fetching by default
  fetch/clone: detect dubious ownership of local repositories
  ...

14 files changed, 502 insertions, 2 deletions

diff --git a/t/helper/test-path-utils.c b/t/helper/test-path-utils.c
index f69709d674..0e0de21807 100644
--- a/t/helper/test-path-utils.c
+++ b/t/helper/test-path-utils.c
@@ -495,6 +495,16 @@ int cmd__path_utils(int argc, const char **argv)
 		return !!res;
 	}
 
+	if (argc == 4 && !strcmp(argv[1], "do_files_match")) {
+		int ret = do_files_match(argv[2], argv[3]);
+
+		if (ret)
+			printf("equal\n");
+		else
+			printf("different\n");
+		return !ret;
+	}
+
 	fprintf(stderr, "%s: unknown function name: %s\n", argv[0],
 		argv[1] ? argv[1] : "(there was none)");
 	return 1;
diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 8ea31d187a..402b201b5a 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh
@@ -1201,6 +1201,34 @@ test_expect_success 'very long name in the index handled sanely' '
 	test $len = 4098
 '
 
+# D/F conflict checking uses an optimization when adding to the end.
+# make sure it does not get confused by `a-` sorting _between_
+# `a` and `a/`.
+test_expect_success 'more update-index D/F conflicts' '
+	# empty the index to make sure our entry is last
+	git read-tree --empty &&
+	cacheinfo=100644,$(test_oid empty_blob) &&
+	git update-index --add --cacheinfo $cacheinfo,path5/a &&
+
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/c/file &&
+
+	# "a-" sorts between "a" and "a/"
+	git update-index --add --cacheinfo $cacheinfo,path5/a- &&
+
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/c/file &&
+
+	cat >expected <<-\EOF &&
+	path5/a
+	path5/a-
+	EOF
+	git ls-files >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'test_must_fail on a failing git command' '
 	test_must_fail git notacommand
 '
diff --git a/t/t0033-safe-directory.sh b/t/t0033-safe-directory.sh
index dc3496897a..11c3e8f28e 100755
--- a/t/t0033-safe-directory.sh
+++ b/t/t0033-safe-directory.sh
@@ -80,4 +80,28 @@ test_expect_success 'safe.directory in included file' '
 	git status
 '
 
+test_expect_success 'local clone of unowned repo refused in unsafe directory' '
+	test_when_finished "rm -rf source" &&
+	git init source &&
+	(
+		sane_unset GIT_TEST_ASSUME_DIFFERENT_OWNER &&
+		test_commit -C source initial
+	) &&
+	test_must_fail git clone --local source target &&
+	test_path_is_missing target
+'
+
+test_expect_success 'local clone of unowned repo accepted in safe directory' '
+	test_when_finished "rm -rf source" &&
+	git init source &&
+	(
+		sane_unset GIT_TEST_ASSUME_DIFFERENT_OWNER &&
+		test_commit -C source initial
+	) &&
+	test_must_fail git clone --local source target &&
+	git config --global --add safe.directory "$(pwd)/source/.git" &&
+	git clone --local source target &&
+	test_path_is_dir target
+'
+
 test_done
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 68e29c904a..73d0e1a7f1 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -560,4 +560,45 @@ test_expect_success !VALGRIND,RUNTIME_PREFIX,CAN_EXEC_IN_PWD '%(prefix)/ works'
 	test_cmp expect actual
 '
 
+test_expect_success 'do_files_match()' '
+	test_seq 0 10 >0-10.txt &&
+	test_seq -1 10 >-1-10.txt &&
+	test_seq 1 10 >1-10.txt &&
+	test_seq 1 9 >1-9.txt &&
+	test_seq 0 8 >0-8.txt &&
+
+	test-tool path-utils do_files_match 0-10.txt 0-10.txt >out &&
+
+	assert_fails() {
+		test_must_fail \
+		test-tool path-utils do_files_match "$1" "$2" >out &&
+		grep different out
+	} &&
+
+	assert_fails 0-8.txt 1-9.txt &&
+	assert_fails -1-10.txt 0-10.txt &&
+	assert_fails 1-10.txt 1-9.txt &&
+	assert_fails 1-10.txt .git &&
+	assert_fails does-not-exist 1-10.txt &&
+
+	if test_have_prereq FILEMODE
+	then
+		cp 0-10.txt 0-10.x &&
+		chmod a+x 0-10.x &&
+		assert_fails 0-10.txt 0-10.x
+	fi &&
+
+	if test_have_prereq SYMLINKS
+	then
+		ln -sf 0-10.txt symlink &&
+		ln -s 0-10.txt another-symlink &&
+		ln -s over-the-ocean yet-another-symlink &&
+		ln -s "$PWD/0-10.txt" absolute-symlink &&
+		assert_fails 0-10.txt symlink &&
+		test-tool path-utils do_files_match symlink another-symlink &&
+		assert_fails symlink yet-another-symlink &&
+		assert_fails symlink absolute-symlink
+	fi
+'
+
 test_done
diff --git a/t/t0411-clone-from-partial.sh b/t/t0411-clone-from-partial.sh
new file mode 100755
index 0000000000..b3d6ddc4bc
--- /dev/null
+++ b/t/t0411-clone-from-partial.sh
@@ -0,0 +1,78 @@
+#!/bin/sh
+
+test_description='check that local clone does not fetch from promisor remotes'
+
+. ./test-lib.sh
+
+test_expect_success 'create evil repo' '
+	git init tmp &&
+	test_commit -C tmp a &&
+	git -C tmp config uploadpack.allowfilter 1 &&
+	git clone --filter=blob:none --no-local --no-checkout tmp evil &&
+	rm -rf tmp &&
+
+	git -C evil config remote.origin.uploadpack \"\$TRASH_DIRECTORY/fake-upload-pack\" &&
+	write_script fake-upload-pack <<-\EOF &&
+		echo >&2 "fake-upload-pack running"
+		>"$TRASH_DIRECTORY/script-executed"
+		exit 1
+	EOF
+	export TRASH_DIRECTORY &&
+
+	# empty shallow file disables local clone optimization
+	>evil/.git/shallow
+'
+
+test_expect_success 'local clone must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git clone \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		evil clone1 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'clone from file://... must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git clone \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		"file://$(pwd)/evil" clone2 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'fetch from file://... must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git fetch \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		"file://$(pwd)/evil" 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'pack-objects should fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	echo "HEAD" | test_must_fail git -C evil pack-objects --revs --stdout >/dev/null 2>err &&
+	grep "fake-upload-pack running" err &&
+	test_path_is_file script-executed
+'
+
+test_expect_success 'clone from promisor remote does not lazy-fetch by default' '
+	rm -f script-executed &&
+	test_must_fail git clone evil no-lazy 2>err &&
+	grep "lazy fetching disabled" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'promisor lazy-fetching can be re-enabled' '
+	rm -f script-executed &&
+	test_must_fail env GIT_NO_LAZY_FETCH=0 \
+		git clone evil lazy-ok 2>err &&
+	grep "fake-upload-pack running" err &&
+	test_path_is_file script-executed
+'
+
+test_done
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index fdb886dfe4..6277ce6b20 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -1023,4 +1023,41 @@ test_expect_success 'fsck error on gitattributes with excessive size' '
 	test_cmp expected actual
 '
 
+test_expect_success 'fsck warning on symlink target with excessive length' '
+	symlink_target=$(printf "pattern %032769d" 1 | git hash-object -w --stdin) &&
+	test_when_finished "remove_object $symlink_target" &&
+	tree=$(printf "120000 blob %s\t%s\n" $symlink_target symlink | git mktree) &&
+	test_when_finished "remove_object $tree" &&
+	cat >expected <<-EOF &&
+	warning in blob $symlink_target: symlinkTargetLength: symlink target too long
+	EOF
+	git fsck --no-dangling >actual 2>&1 &&
+	test_cmp expected actual
+'
+
+test_expect_success 'fsck warning on symlink target pointing inside git dir' '
+	gitdir=$(printf ".git" | git hash-object -w --stdin) &&
+	ntfs_gitdir=$(printf "GIT~1" | git hash-object -w --stdin) &&
+	hfs_gitdir=$(printf ".${u200c}git" | git hash-object -w --stdin) &&
+	inside_gitdir=$(printf "nested/.git/config" | git hash-object -w --stdin) &&
+	benign_target=$(printf "legit/config" | git hash-object -w --stdin) &&
+	tree=$(printf "120000 blob %s\t%s\n" \
+		$benign_target benign_target \
+		$gitdir gitdir \
+		$hfs_gitdir hfs_gitdir \
+		$inside_gitdir inside_gitdir \
+		$ntfs_gitdir ntfs_gitdir |
+		git mktree) &&
+	for o in $gitdir $ntfs_gitdir $hfs_gitdir $inside_gitdir $benign_target $tree
+	do
+		test_when_finished "remove_object $o" || return 1
+	done &&
+	printf "warning in blob %s: symlinkPointsToGitDir: symlink target points to git dir\n" \
+		$gitdir $hfs_gitdir $inside_gitdir $ntfs_gitdir |
+	sort >expected &&
+	git fsck --no-dangling >actual 2>&1 &&
+	sort actual >actual.sorted &&
+	test_cmp expected actual.sorted
+'
+
 test_done
diff --git a/t/t1800-hook.sh b/t/t1800-hook.sh
index 3506f627b6..0f0c706d07 100755
--- a/t/t1800-hook.sh
+++ b/t/t1800-hook.sh
@@ -195,4 +195,19 @@ test_expect_success 'stdin to hooks' '
 	test_cmp expect actual
 '
 
+test_expect_success 'clone protections' '
+	test_config core.hooksPath "$(pwd)/my-hooks" &&
+	mkdir -p my-hooks &&
+	write_script my-hooks/test-hook <<-\EOF &&
+	echo Hook ran $1
+	EOF
+
+	git hook run test-hook 2>err &&
+	grep "Hook ran" err &&
+	test_must_fail env GIT_CLONE_PROTECTION_ACTIVE=true \
+		git hook run test-hook 2>err &&
+	grep "active .core.hooksPath" err &&
+	! grep "Hook ran" err
+'
+
 test_done
diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index 34a1261520..854ebd3542 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -1248,6 +1248,30 @@ EOF
 	test_cmp fatal-expect fatal-actual
 '
 
+test_expect_success SYMLINKS 'clone does not get confused by a D/F conflict' '
+	git init df-conflict &&
+	(
+		cd df-conflict &&
+		ln -s .git a &&
+		git add a &&
+		test_tick &&
+		git commit -m symlink &&
+		test_commit a- &&
+		rm a &&
+		mkdir -p a/hooks &&
+		write_script a/hooks/post-checkout <<-EOF &&
+		echo WHOOPSIE >&2
+		echo whoopsie >"$TRASH_DIRECTORY"/whoops
+		EOF
+		git add a/hooks/post-checkout &&
+		test_tick &&
+		git commit -m post-checkout
+	) &&
+	git clone df-conflict clone 2>err &&
+	! grep WHOOPS err &&
+	test_path_is_missing whoops
+'
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd
 
diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh
index b7d5551262..1bcf652b10 100755
--- a/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@ -633,6 +633,21 @@ test_expect_success CASE_INSENSITIVE_FS 'colliding file detection' '
 	test_i18ngrep "the following paths have collided" icasefs/warning
 '
 
+test_expect_success CASE_INSENSITIVE_FS,SYMLINKS \
+		'colliding symlink/directory keeps directory' '
+	git init icasefs-colliding-symlink &&
+	(
+		cd icasefs-colliding-symlink &&
+		a=$(printf a | git hash-object -w --stdin) &&
+		printf "100644 %s 0\tA/dir/b\n120000 %s 0\ta\n" $a $a >idx &&
+		git update-index --index-info <idx &&
+		test_tick &&
+		git commit -m initial
+	) &&
+	git clone icasefs-colliding-symlink icasefs-colliding-symlink-clone &&
+	test_file_not_empty icasefs-colliding-symlink-clone/A/dir/b
+'
+
 test_expect_success 'clone with GIT_DEFAULT_HASH' '
 	(
 		sane_unset GIT_DEFAULT_HASH &&
@@ -756,6 +771,57 @@ test_expect_success 'batch missing blob request does not inadvertently try to fe
 	git clone --filter=blob:limit=0 "file://$(pwd)/server" client
 '
 
+test_expect_success 'clone with init.templatedir runs hooks' '
+	git init tmpl/hooks &&
+	write_script tmpl/hooks/post-checkout <<-EOF &&
+	echo HOOK-RUN >&2
+	echo I was here >hook.run
+	EOF
+	git -C tmpl/hooks add . &&
+	test_tick &&
+	git -C tmpl/hooks commit -m post-checkout &&
+
+	test_when_finished "git config --global --unset init.templateDir || :" &&
+	test_when_finished "git config --unset init.templateDir || :" &&
+	(
+		sane_unset GIT_TEMPLATE_DIR &&
+		NO_SET_GIT_TEMPLATE_DIR=t &&
+		export NO_SET_GIT_TEMPLATE_DIR &&
+
+		git -c core.hooksPath="$(pwd)/tmpl/hooks" \
+			clone tmpl/hooks hook-run-hookspath 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-hookspath/hook.run &&
+
+		git -c init.templateDir="$(pwd)/tmpl" \
+			clone tmpl/hooks hook-run-config 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-config/hook.run &&
+
+		git clone --template=tmpl tmpl/hooks hook-run-option 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-option/hook.run &&
+
+		git config --global init.templateDir "$(pwd)/tmpl" &&
+		git clone tmpl/hooks hook-run-global-config 2>err &&
+		git config --global --unset init.templateDir &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-global-config/hook.run &&
+
+		# clone ignores local `init.templateDir`; need to create
+		# a new repository because we deleted `.git/` in the
+		# `setup` test case above
+		git init local-clone &&
+		cd local-clone &&
+
+		git config init.templateDir "$(pwd)/../tmpl" &&
+		git clone ../tmpl/hooks hook-run-local-config 2>err &&
+		git config --unset init.templateDir &&
+		! grep "active .* hook found" err &&
+		test_path_is_missing hook-run-local-config/hook.run
+	)
+'
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd
 
diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index eae6a46ef3..3e8cf9b885 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh
@@ -1436,4 +1436,35 @@ test_expect_success 'recursive clone respects -q' '
 	test_must_be_empty actual
 '
 
+test_expect_success '`submodule init` and `init.templateDir`' '
+	mkdir -p tmpl/hooks &&
+	write_script tmpl/hooks/post-checkout <<-EOF &&
+	echo HOOK-RUN >&2
+	echo I was here >hook.run
+	exit 1
+	EOF
+
+	test_config init.templateDir "$(pwd)/tmpl" &&
+	test_when_finished \
+		"git config --global --unset init.templateDir || true" &&
+	(
+		sane_unset GIT_TEMPLATE_DIR &&
+		NO_SET_GIT_TEMPLATE_DIR=t &&
+		export NO_SET_GIT_TEMPLATE_DIR &&
+
+		git config --global init.templateDir "$(pwd)/tmpl" &&
+		test_must_fail git submodule \
+			add "$submodurl" sub-global 2>err &&
+		git config --global --unset init.templateDir &&
+		grep HOOK-RUN err &&
+		test_path_is_file sub-global/hook.run &&
+
+		git config init.templateDir "$(pwd)/tmpl" &&
+		git submodule add "$submodurl" sub-local 2>err &&
+		git config --unset init.templateDir &&
+		! grep HOOK-RUN err &&
+		test_path_is_missing sub-local/hook.run
+	)
+'
+
 test_done
diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index f094e3d7f3..dae87090e0 100755
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -1179,4 +1179,52 @@ test_expect_success 'submodule update --recursive skip submodules with strategy=
 	test_cmp expect.err actual.err
 '
 
+test_expect_success CASE_INSENSITIVE_FS,SYMLINKS \
+	'submodule paths must not follow symlinks' '
+
+	# This is only needed because we want to run this in a self-contained
+	# test without having to spin up an HTTP server; However, it would not
+	# be needed in a real-world scenario where the submodule is simply
+	# hosted on a public site.
+	test_config_global protocol.file.allow always &&
+
+	# Make sure that Git tries to use symlinks on Windows
+	test_config_global core.symlinks true &&
+
+	tell_tale_path="$PWD/tell.tale" &&
+	git init hook &&
+	(
+		cd hook &&
+		mkdir -p y/hooks &&
+		write_script y/hooks/post-checkout <<-EOF &&
+		echo HOOK-RUN >&2
+		echo hook-run >"$tell_tale_path"
+		EOF
+		git add y/hooks/post-checkout &&
+		test_tick &&
+		git commit -m post-checkout
+	) &&
+
+	hook_repo_path="$(pwd)/hook" &&
+	git init captain &&
+	(
+		cd captain &&
+		git submodule add --name x/y "$hook_repo_path" A/modules/x &&
+		test_tick &&
+		git commit -m add-submodule &&
+
+		printf .git >dotgit.txt &&
+		git hash-object -w --stdin <dotgit.txt >dot-git.hash &&
+		printf "120000 %s 0\ta\n" "$(cat dot-git.hash)" >index.info &&
+		git update-index --index-info <index.info &&
+		test_tick &&
+		git commit -m add-symlink
+	) &&
+
+	test_path_is_missing "$tell_tale_path" &&
+	git clone --recursive captain hooked 2>err &&
+	! grep HOOK-RUN err &&
+	test_path_is_missing "$tell_tale_path"
+'
+
 test_done
diff --git a/t/t7423-submodule-symlinks.sh b/t/t7423-submodule-symlinks.sh
new file mode 100755
index 0000000000..3d3c7af3ce
--- /dev/null
+++ b/t/t7423-submodule-symlinks.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+
+test_description='check that submodule operations do not follow symlinks'
+
+. ./test-lib.sh
+
+test_expect_success 'prepare' '
+	git config --global protocol.file.allow always &&
+	test_commit initial &&
+	git init upstream &&
+	test_commit -C upstream upstream submodule_file &&
+	git submodule add ./upstream a/sm &&
+	test_tick &&
+	git commit -m submodule
+'
+
+test_expect_success SYMLINKS 'git submodule update must not create submodule behind symlink' '
+	rm -rf a b &&
+	mkdir b &&
+	ln -s b a &&
+	test_path_is_missing b/sm &&
+	test_must_fail git submodule update &&
+	test_path_is_missing b/sm
+'
+
+test_expect_success SYMLINKS,CASE_INSENSITIVE_FS 'git submodule update must not create submodule behind symlink on case insensitive fs' '
+	rm -rf a b &&
+	mkdir b &&
+	ln -s b A &&
+	test_must_fail git submodule update &&
+	test_path_is_missing b/sm
+'
+
+prepare_symlink_to_repo() {
+	rm -rf a &&
+	mkdir a &&
+	git init a/target &&
+	git -C a/target fetch ../../upstream &&
+	ln -s target a/sm
+}
+
+test_expect_success SYMLINKS 'git restore --recurse-submodules must not be confused by a symlink' '
+	prepare_symlink_to_repo &&
+	test_must_fail git restore --recurse-submodules a/sm &&
+	test_path_is_missing a/sm/submodule_file &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing a/target/submodule_file
+'
+
+test_expect_success SYMLINKS 'git restore --recurse-submodules must not migrate git dir of symlinked repo' '
+	prepare_symlink_to_repo &&
+	rm -rf .git/modules &&
+	test_must_fail git restore --recurse-submodules a/sm &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing .git/modules/a/sm &&
+	test_path_is_missing a/target/submodule_file
+'
+
+test_expect_success SYMLINKS 'git checkout -f --recurse-submodules must not migrate git dir of symlinked repo when removing submodule' '
+	prepare_symlink_to_repo &&
+	rm -rf .git/modules &&
+	test_must_fail git checkout -f --recurse-submodules initial &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing .git/modules/a/sm
+'
+
+test_done
diff --git a/t/t7450-bad-git-dotfiles.sh b/t/t7450-bad-git-dotfiles.sh
index 0d0c3f2c68..60d627583d 100755
--- a/t/t7450-bad-git-dotfiles.sh
+++ b/t/t7450-bad-git-dotfiles.sh
@@ -294,7 +294,7 @@ test_expect_success WINDOWS 'prevent git~1 squatting on Windows' '
 	fi
 '
 
-test_expect_success 'git dirs of sibling submodules must not be nested' '
+test_expect_success 'setup submodules with nested git dirs' '
 	git init nested &&
 	test_commit -C nested nested &&
 	(
@@ -312,9 +312,39 @@ test_expect_success 'git dirs of sibling submodules must not be nested' '
 		git add .gitmodules thing1 thing2 &&
 		test_tick &&
 		git commit -m nested
-	) &&
+	)
+'
+
+test_expect_success 'git dirs of sibling submodules must not be nested' '
 	test_must_fail git clone --recurse-submodules nested clone 2>err &&
 	test_i18ngrep "is inside git dir" err
 '
 
+test_expect_success 'submodule git dir nesting detection must work with parallel cloning' '
+	test_must_fail git clone --recurse-submodules --jobs=2 nested clone_parallel 2>err &&
+	cat err &&
+	grep -E "(already exists|is inside git dir|not a git repository)" err &&
+	{
+		test_path_is_missing .git/modules/hippo/HEAD ||
+		test_path_is_missing .git/modules/hippo/hooks/HEAD
+	}
+'
+
+test_expect_success 'checkout -f --recurse-submodules must not use a nested gitdir' '
+	git clone nested nested_checkout &&
+	(
+		cd nested_checkout &&
+		git submodule init &&
+		git submodule update thing1 &&
+		mkdir -p .git/modules/hippo/hooks/refs &&
+		mkdir -p .git/modules/hippo/hooks/objects/info &&
+		echo "../../../../objects" >.git/modules/hippo/hooks/objects/info/alternates &&
+		echo "ref: refs/heads/master" >.git/modules/hippo/hooks/HEAD
+	) &&
+	test_must_fail git -C nested_checkout checkout -f --recurse-submodules HEAD 2>err &&
+	cat err &&
+	grep "is inside git dir" err &&
+	test_path_is_missing nested_checkout/thing2/.git
+'
+
 test_done
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 62136caee5..93df6d6545 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -334,6 +334,7 @@ nr_san_dir_leaks_ () {
 	find "$TEST_RESULTS_SAN_DIR" \
 		-type f \
 		-name "$TEST_RESULTS_SAN_FILE_PFX.*" 2>/dev/null |
+	xargs grep -lv "Unable to get registers from thread" |
 	wc -l
 }