merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/t/t2006-checkout-index-basic.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+test_description='basic checkout-index tests
+'
+
+. ./test-lib.sh
+
+test_expect_success 'checkout-index --gobbledegook' '
+	test_expect_code 129 git checkout-index --gobbledegook 2>err &&
+	test_i18ngrep "[Uu]sage" err
+'
+
+test_expect_success 'checkout-index -h in broken repository' '
+	mkdir broken &&
+	(
+		cd broken &&
+		git init &&
+		>.git/index &&
+		test_expect_code 129 git checkout-index -h >usage 2>&1
+	) &&
+	test_i18ngrep "[Uu]sage" broken/usage
+'
+
+test_done