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

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

third_party/git/t/t6028-merge-up-to-date.sh

@@ -0,0 +1,92 @@
+#!/bin/sh
+
+test_description='merge fast-forward and up to date'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	>file &&
+	git add file &&
+	test_tick &&
+	git commit -m initial &&
+	git tag c0 &&
+
+	echo second >file &&
+	git add file &&
+	test_tick &&
+	git commit -m second &&
+	git tag c1 &&
+	git branch test &&
+	echo third >file &&
+	git add file &&
+	test_tick &&
+	git commit -m third &&
+	git tag c2
+'
+
+test_expect_success 'merge -s recursive up-to-date' '
+
+	git reset --hard c1 &&
+	test_tick &&
+	git merge -s recursive c0 &&
+	expect=$(git rev-parse c1) &&
+	current=$(git rev-parse HEAD) &&
+	test "$expect" = "$current"
+
+'
+
+test_expect_success 'merge -s recursive fast-forward' '
+
+	git reset --hard c0 &&
+	test_tick &&
+	git merge -s recursive c1 &&
+	expect=$(git rev-parse c1) &&
+	current=$(git rev-parse HEAD) &&
+	test "$expect" = "$current"
+
+'
+
+test_expect_success 'merge -s ours up-to-date' '
+
+	git reset --hard c1 &&
+	test_tick &&
+	git merge -s ours c0 &&
+	expect=$(git rev-parse c1) &&
+	current=$(git rev-parse HEAD) &&
+	test "$expect" = "$current"
+
+'
+
+test_expect_success 'merge -s ours fast-forward' '
+
+	git reset --hard c0 &&
+	test_tick &&
+	git merge -s ours c1 &&
+	expect=$(git rev-parse c0^{tree}) &&
+	current=$(git rev-parse HEAD^{tree}) &&
+	test "$expect" = "$current"
+
+'
+
+test_expect_success 'merge -s subtree up-to-date' '
+
+	git reset --hard c1 &&
+	test_tick &&
+	git merge -s subtree c0 &&
+	expect=$(git rev-parse c1) &&
+	current=$(git rev-parse HEAD) &&
+	test "$expect" = "$current"
+
+'
+
+test_expect_success 'merge fast-forward octopus' '
+
+	git reset --hard c0 &&
+	test_tick &&
+	git merge c1 c2 &&
+	expect=$(git rev-parse c2) &&
+	current=$(git rev-parse HEAD) &&
+	test "$expect" = "$current"
+'
+
+test_done