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

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

third_party/git/t/t3050-subprojects-fetch.sh

@@ -0,0 +1,52 @@
+#!/bin/sh
+
+test_description='fetching and pushing project with subproject'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_tick &&
+	mkdir -p sub && (
+		cd sub &&
+		git init &&
+		>subfile &&
+		git add subfile &&
+		git commit -m "subproject commit #1"
+	) &&
+	>mainfile &&
+	git add sub mainfile &&
+	test_tick &&
+	git commit -m "superproject commit #1"
+'
+
+test_expect_success clone '
+	git clone "file://$(pwd)/.git" cloned &&
+	(git rev-parse HEAD && git ls-files -s) >expected &&
+	(
+		cd cloned &&
+		(git rev-parse HEAD && git ls-files -s) >../actual
+	) &&
+	test_cmp expected actual
+'
+
+test_expect_success advance '
+	echo more >mainfile &&
+	git update-index --force-remove sub &&
+	mv sub/.git sub/.git-disabled &&
+	git add sub/subfile mainfile &&
+	mv sub/.git-disabled sub/.git &&
+	test_tick &&
+	git commit -m "superproject commit #2"
+'
+
+test_expect_success fetch '
+	(git rev-parse HEAD && git ls-files -s) >expected &&
+	(
+		cd cloned &&
+		git pull &&
+		(git rev-parse HEAD && git ls-files -s) >../actual
+	) &&
+	test_cmp expected actual
+'
+
+test_done