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diff --git a/t/t2011-checkout-invalid-head.sh b/t/t2011-checkout-invalid-head.sh
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+++ b/t/t2011-checkout-invalid-head.sh
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+#!/bin/sh
+
+test_description='checkout switching away from an invalid branch'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+TEST_PASSES_SANITIZE_LEAK=true
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo hello >world &&
+	git add world &&
+	git commit -m initial
+'
+
+test_expect_success 'checkout should not start branch from a tree' '
+	test_must_fail git checkout -b newbranch main^{tree}
+'
+
+test_expect_success 'checkout main from invalid HEAD' '
+	echo $ZERO_OID >.git/HEAD &&
+	git checkout main --
+'
+
+test_expect_success 'checkout notices failure to lock HEAD' '
+	test_when_finished "rm -f .git/HEAD.lock" &&
+	>.git/HEAD.lock &&
+	test_must_fail git checkout -b other
+'
+
+test_expect_success 'create ref directory/file conflict scenario' '
+	git update-ref refs/heads/outer/inner main &&
+
+	# do not rely on symbolic-ref to get a known state,
+	# as it may use the same code we are testing
+	reset_to_df () {
+		echo "ref: refs/heads/outer" >.git/HEAD
+	}
+'
+
+test_expect_success 'checkout away from d/f HEAD (unpacked, to branch)' '
+	reset_to_df &&
+	git checkout main
+'
+
+test_expect_success 'checkout away from d/f HEAD (unpacked, to detached)' '
+	reset_to_df &&
+	git checkout --detach main
+'
+
+test_expect_success 'pack refs' '
+	git pack-refs --all --prune
+'
+
+test_expect_success 'checkout away from d/f HEAD (packed, to branch)' '
+	reset_to_df &&
+	git checkout main
+'
+
+test_expect_success 'checkout away from d/f HEAD (packed, to detached)' '
+	reset_to_df &&
+	git checkout --detach main
+'
+test_done