Parse merge conflict format for multi diffs.

dart/tests/try/poi/source_update_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Test [source_update.dart].
 library trydart.source_update_test;
 
 import 'dart:convert' show
     JSON;
 
 import 'package:expect/expect.dart' show
     Expect;
 
 import 'source_update.dart' show
+    expandDiff,
     expandUpdates,
     splitFiles,
     splitLines;
 
 main() {
   Expect.listEquals(
       ["head v1 tail", "head v2 tail"],
       expandUpdates(["head ", ["v1", "v2"], " tail"]));
 
   Expect.listEquals(
@@ skipping 36 matching lines @@
 
   Expect.stringEquals("{}", JSON.encode(splitFiles("")));
 
   Expect.stringEquals("[]", JSON.encode(splitLines("")));
 
   Expect.stringEquals('["1"]', JSON.encode(splitLines("1")));
 
   Expect.stringEquals('["\\n"]', JSON.encode(splitLines("\n")));
 
   Expect.stringEquals('["\\n","1"]', JSON.encode(splitLines("\n1")));
+
+  Expect.stringEquals(
+      '["","",""]',
+      JSON.encode(expandUpdates(expandDiff(r"""
+<<<<<<<
+=======
+=======
+>>>>>>>
+"""))));
+
+  Expect.stringEquals(
+      r'["first\nv1\nlast\n","first\nv2\nlast\n","first\nv3\nlast\n"]',
+      JSON.encode(expandUpdates(expandDiff(r"""
+first
+<<<<<<<
+v1
+=======
+v2
+=======
+v3
+>>>>>>>
+last
+"""))));
+
+  Expect.stringEquals(
+      r'["v1\nlast\n","v2\nlast\n","v3\nlast\n"]',
+      JSON.encode(expandUpdates(expandDiff(r"""
+<<<<<<<
+v1
+=======
+v2
+=======
+v3
+>>>>>>>
+last
+"""))));
+
+  Expect.stringEquals(
+      r'["v1\n","v2\n","v3\n"]',
+      JSON.encode(expandUpdates(expandDiff(r"""
+<<<<<<<
+v1
+=======
+v2
+=======
+v3
+>>>>>>>
+"""))));
 }