t3431: add rebase --fork-point tests

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Denton-L

t/t3431-rebase-fork-point.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Denton Liu
+#
+
+test_description='git rebase --fork-point test'
+
+. ./test-lib.sh
+
+# A---B---D---E    (master)
+#      \
+#       C*---F---G (side)
+#
+# C was formerly part of master but master was rewound to remove C
+#
+test_expect_success setup '
+	test_commit A &&
+	test_commit B &&
+	test_commit C &&
+	git branch -t side &&
+	git reset --hard HEAD^ &&
+	test_commit D &&
+	test_commit E &&
+	git checkout side &&
+	test_commit F &&
+	test_commit G
+'
+
+test_rebase () {
+	expected="$1" &&
+	shift &&
+	test_expect_success "git rebase $*" "
+		git checkout master &&
+		git reset --hard E &&
+		git checkout side &&
+		git reset --hard G &&
+		git rebase $* &&
+		test_write_lines $expected >expect &&
+		git log --pretty=%s >actual &&
+		test_cmp expect actual
+	"
+}
+
+test_rebase 'G F E D B A'
+test_rebase 'G F D B A' --onto D
+test_rebase 'G F C E D B A' --no-fork-point
+test_rebase 'G F C D B A' --no-fork-point --onto D
+test_rebase 'G F E D B A' --fork-point refs/heads/master
+test_rebase 'G F D B A' --fork-point --onto D refs/heads/master
+test_rebase 'G F C E D B A' refs/heads/master
+test_rebase 'G F C D B A' --onto D refs/heads/master
+
+test_done