1 files changed, 61 insertions, 0 deletions
diff --git a/third_party/git/t/t2011-checkout-invalid-head.sh b/third_party/git/t/t2011-checkout-invalid-head.sh
new file mode 100755
index 000000000000..0e8d56aa7631
--- /dev/null
+++ b/third_party/git/t/t2011-checkout-invalid-head.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+
+test_description='checkout switching away from an invalid branch'
+
+. ./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 master^{tree}
+'
+
+test_expect_success 'checkout master from invalid HEAD' '
+	echo $ZERO_OID >.git/HEAD &&
+	git checkout master --
+'
+
+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 master &&
+
+	# 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 master
+'
+
+test_expect_success 'checkout away from d/f HEAD (unpacked, to detached)' '
+	reset_to_df &&
+	git checkout --detach master
+'
+
+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 master
+'
+
+test_expect_success 'checkout away from d/f HEAD (packed, to detached)' '
+	reset_to_df &&
+	git checkout --detach master
+'
+test_done