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

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

third_party/git/t/t4134-apply-submodule.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Peter Collingbourne
+#
+
+test_description='git apply submodule tests'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	cat > create-sm.patch <<EOF &&
+diff --git a/dir/sm b/dir/sm
+new file mode 160000
+index 0000000..0123456
+--- /dev/null
++++ b/dir/sm
+@@ -0,0 +1 @@
++Subproject commit 0123456789abcdef0123456789abcdef01234567
+EOF
+	cat > remove-sm.patch <<EOF
+diff --git a/dir/sm b/dir/sm
+deleted file mode 160000
+index 0123456..0000000
+--- a/dir/sm
++++ /dev/null
+@@ -1 +0,0 @@
+-Subproject commit 0123456789abcdef0123456789abcdef01234567
+EOF
+'
+
+test_expect_success 'removing a submodule also removes all leading subdirectories' '
+	git apply --index create-sm.patch &&
+	test -d dir/sm &&
+	git apply --index remove-sm.patch &&
+	test \! -d dir
+'
+
+test_done