t6042: add testcase covering rename/rename(2to1)/delete/delete conflict

If either side of a rename/rename(2to1) conflict is itself also involved
in a rename/delete conflict, then the conflict is a little more complex;
we can even have what I'd call a rename/rename(2to1)/delete/delete
conflict.  (In some ways, this is similar to a rename/rename(1to2)/add/add
conflict, as added in commit 3672c97148 ("merge-recursive: Fix working
copy handling for rename/rename/add/add", 2011-08-11)).  Add a testcase
for such a conflict.

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

t/t6042-merge-rename-corner-cases.sh

@@ -759,4 +759,72 @@ test_expect_failure 'rad-check: rename/add/delete conflict' '
 	)
 '
 
+# Testcase rrdd, rename/rename(2to1)/delete/delete
+#   Commit O: foo, bar
+#   Commit A: rename foo->baz, rm bar
+#   Commit B: rename bar->baz, rm foo
+#   Expected: CONFLICT (rename/rename/delete/delete), two-way merged baz
+
+test_expect_success 'rrdd-setup: rename/rename(2to1)/delete/delete conflict' '
+	test_create_repo rrdd &&
+	(
+		cd rrdd &&
+		echo foo >foo &&
+		echo bar >bar &&
+		git add foo bar &&
+		git commit -m O &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		git mv foo baz &&
+		git rm bar &&
+		git commit -m "Rename foo, remove bar" &&
+
+		git checkout B &&
+		git mv bar baz &&
+		git rm foo &&
+		git commit -m "Rename bar, remove foo"
+	)
+'
+
+test_expect_failure 'rrdd-check: rename/rename(2to1)/delete/delete conflict' '
+	(
+		cd rrdd &&
+
+		git checkout A^0 &&
+		test_must_fail git merge -s recursive B^0 >out 2>err &&
+
+		# Not sure whether the output should contain just one
+		# "CONFLICT (rename/rename/delete/delete)" line, or if it
+		# should break it into three: "CONFLICT (rename/rename)" and
+		# two "CONFLICT (rename/delete)" lines; allow for either.
+		test_i18ngrep "CONFLICT (rename/rename)" out &&
+		test_i18ngrep "CONFLICT (rename.*delete)" out &&
+		test_must_be_empty err &&
+
+		git ls-files -s >file_count &&
+		test_line_count = 2 file_count &&
+		git ls-files -u >file_count &&
+		test_line_count = 2 file_count &&
+		git ls-files -o >file_count &&
+		test_line_count = 2 file_count &&
+
+		git rev-parse >actual \
+			:2:baz :3:baz &&
+		git rev-parse >expect \
+			O:foo  O:bar  &&
+
+		test_cmp file_is_missing foo &&
+		test_cmp file_is_missing bar &&
+		# baz should have two-way merged contents of the original
+		# contents of foo and bar; check that content from both sides
+		# is present.
+		grep foo baz &&
+		grep bar baz
+	)
+'
+
 test_done