t3401: add directory rename testcases for rebase and am

Add a simple directory rename testcase, in conjunction with each of the
types of rebases:
  git-rebase--interactive
  git-rebase--am
  git-rebase--merge
and also use the same testcase for
  git am --3way

This demonstrates a difference in behavior between the different rebase
backends in regards to directory rename detection.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3401-rebase-and-am-rename.sh

+#!/bin/sh
+
+test_description='git rebase + directory rename tests'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-rebase.sh
+
+test_expect_success 'setup testcase' '
+	test_create_repo dir-rename &&
+	(
+		cd dir-rename &&
+
+		mkdir x &&
+		test_seq  1 10 >x/a &&
+		test_seq 11 20 >x/b &&
+		test_seq 21 30 >x/c &&
+		test_write_lines a b c d e f g h i >l &&
+		git add x l &&
+		git commit -m "Initial" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		git mv x y &&
+		git mv l letters &&
+		git commit -m "Rename x to y, l to letters" &&
+
+		git checkout B &&
+		echo j >>l &&
+		test_seq 31 40 >x/d &&
+		git add l x/d &&
+		git commit -m "Modify l, add x/d"
+	)
+'
+
+test_expect_success 'rebase --interactive: directory rename detected' '
+	(
+		cd dir-rename &&
+
+		git checkout B^0 &&
+
+		set_fake_editor &&
+		FAKE_LINES="1" git rebase --interactive A &&
+
+		git ls-files -s >out &&
+		test_line_count = 5 out &&
+
+		test_path_is_file y/d &&
+		test_path_is_missing x/d
+	)
+'
+
+test_expect_failure 'rebase (am): directory rename detected' '
+	(
+		cd dir-rename &&
+
+		git checkout B^0 &&
+
+		git rebase A &&
+
+		git ls-files -s >out &&
+		test_line_count = 5 out &&
+
+		test_path_is_file y/d &&
+		test_path_is_missing x/d
+	)
+'
+
+test_expect_success 'rebase --merge: directory rename detected' '
+	(
+		cd dir-rename &&
+
+		git checkout B^0 &&
+
+		git rebase --merge A &&
+
+		git ls-files -s >out &&
+		test_line_count = 5 out &&
+
+		test_path_is_file y/d &&
+		test_path_is_missing x/d
+	)
+'
+
+test_expect_failure 'am: directory rename detected' '
+	(
+		cd dir-rename &&
+
+		git checkout A^0 &&
+
+		git format-patch -1 B &&
+
+		git am --3way 0001*.patch &&
+
+		git ls-files -s >out &&
+		test_line_count = 5 out &&
+
+		test_path_is_file y/d &&
+		test_path_is_missing x/d
+	)
+'
+
+test_done