Add tests for several double-dash scenarios

Double dash (--) should end option sequences, but should have no effect
on value sequences. These unit tests reflect that design.

tests/CommandLine.Tests/Fakes/Options_With_Value_Sequence_And_Subsequent_Value.cs

@@ -0,0 +1,15 @@
+// Copyright 2005-2015 Giacomo Stelluti Scala & Contributors. All rights reserved. See License.md in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace CommandLine.Tests.Fakes
+{
+    class Options_With_Value_Sequence_And_Subsequent_Value
+    {
+        [Value(0)]
+        public IEnumerable<string> StringSequence { get; set; }
+
+        [Value(1)]
+        public string NeverReachedValue { get; set; }
+    }
+}

tests/CommandLine.Tests/Fakes/Options_With_Value_Sequence_With_Max_And_Subsequent_Value.cs

@@ -0,0 +1,15 @@
+// Copyright 2005-2015 Giacomo Stelluti Scala & Contributors. All rights reserved. See License.md in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace CommandLine.Tests.Fakes
+{
+    class Options_With_Value_Sequence_With_Max_And_Subsequent_Value
+    {
+        [Value(0, Max=2)]
+        public IEnumerable<string> StringSequence { get; set; }
+
+        [Value(1)]
+        public string NeverReachedValue { get; set; }
+    }
+}

tests/CommandLine.Tests/Unit/ParserTests.cs

@@ -152,6 +152,77 @@ public void Parse_options_with_double_dash_and_option_sequence()
             ((Parsed<Options_With_Option_Sequence_And_Value_Sequence>)result).Value.Should().BeEquivalentTo(expectedOptions);
         }
 
+        [Theory]
+        [InlineData("value1", "value2", "value3")]
+        [InlineData("--", "value1", "value2", "value3")]
+        [InlineData("value1", "--", "value2", "value3")]
+        [InlineData("value1", "value2", "--", "value3")]
+        [InlineData("value1", "value2", "value3", "--")]
+        public void Parse_options_with_double_dash_in_various_positions(params string[] args)
+        {
+            var expectedOptions = new Options_With_Sequence_And_Only_Max_Constraint_For_Value
+            {
+                StringSequence = new[] { "value1", "value2", "value3" }
+            };
+
+            var sut = new Parser(with => with.EnableDashDash = true);
+
+            // Exercize system
+            var result =
+                sut.ParseArguments<Options_With_Sequence_And_Only_Max_Constraint_For_Value>(args);
+
+            // Verify outcome
+            ((Parsed<Options_With_Sequence_And_Only_Max_Constraint_For_Value>)result).Value.Should().BeEquivalentTo(expectedOptions);
+        }
+
+        [Theory]
+        [InlineData("value1", "value2", "value3")]
+        [InlineData("--", "value1", "value2", "value3")]
+        [InlineData("value1", "--", "value2", "value3")]
+        [InlineData("value1", "value2", "--", "value3")]
+        [InlineData("value1", "value2", "value3", "--")]
+        public void Parse_options_with_double_dash_and_all_consuming_sequence_leaves_nothing_for_later_values(params string[] args)
+        {
+            var expectedOptions = new Options_With_Value_Sequence_And_Subsequent_Value
+            {
+                StringSequence = new[] { "value1", "value2", "value3" },
+                NeverReachedValue = null
+            };
+
+            var sut = new Parser(with => with.EnableDashDash = true);
+
+            // Exercize system
+            var result =
+                sut.ParseArguments<Options_With_Value_Sequence_And_Subsequent_Value>(args);
+
+            // Verify outcome
+            ((Parsed<Options_With_Value_Sequence_And_Subsequent_Value>)result).Value.Should().BeEquivalentTo(expectedOptions);
+        }
+
+        [Theory]
+        [InlineData("value1", "value2", "value3")]
+        [InlineData("--", "value1", "value2", "value3")]
+        [InlineData("value1", "--", "value2", "value3")]
+        [InlineData("value1", "value2", "--", "value3")]
+        [InlineData("value1", "value2", "value3", "--")]
+        public void Parse_options_with_double_dash_and_limited_sequence_leaves_something_for_later_values(params string[] args)
+        {
+            var expectedOptions = new Options_With_Value_Sequence_With_Max_And_Subsequent_Value
+            {
+                StringSequence = new[] { "value1", "value2" },
+                NeverReachedValue = "value3"
+            };
+
+            var sut = new Parser(with => with.EnableDashDash = true);
+
+            // Exercize system
+            var result =
+                sut.ParseArguments<Options_With_Value_Sequence_With_Max_And_Subsequent_Value>(args);
+
+            // Verify outcome
+            ((Parsed<Options_With_Value_Sequence_With_Max_And_Subsequent_Value>)result).Value.Should().BeEquivalentTo(expectedOptions);
+        }
+
         [Fact]
         public void Parse_options_with_double_dash_in_verbs_scenario()
         {