add tests for merging with submodules

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7405-submodule-merge.sh

@@ -0,0 +1,74 @@
+#!/bin/sh
+
+test_description='merging with submodules'
+
+. ./test-lib.sh
+
+#
+# history
+#
+#        a --- c
+#      /   \ /
+# root      X
+#      \   / \
+#        b --- d
+#
+
+test_expect_success setup '
+
+	mkdir sub &&
+	(cd sub &&
+	 git init &&
+	 echo original > file &&
+	 git add file &&
+	 test_tick &&
+	 git commit -m sub-root) &&
+	git add sub &&
+	test_tick &&
+	git commit -m root &&
+
+	git checkout -b a master &&
+	(cd sub &&
+	 echo A > file &&
+	 git add file &&
+	 test_tick &&
+	 git commit -m sub-a) &&
+	git add sub &&
+	test_tick &&
+	git commit -m a &&
+
+	git checkout -b b master &&
+	(cd sub &&
+	 echo B > file &&
+	 git add file &&
+	 test_tick &&
+	 git commit -m sub-b) &&
+	git add sub &&
+	test_tick &&
+	git commit -m b
+
+	git checkout -b c a &&
+	git merge -s ours b &&
+
+	git checkout -b d b &&
+	git merge -s ours a
+'
+
+test_expect_failure 'merging with modify/modify conflict' '
+
+	git checkout -b test1 a &&
+	test_must_fail git merge b &&
+	test -f .git/MERGE_MSG &&
+	git diff
+
+'
+
+test_expect_failure 'merging with a modify/modify conflict between merge bases' '
+
+	git reset --hard HEAD &&
+	git checkout -b test2 c &&
+	git merge d
+
+'
+
+test_done