Add extra test to ensure mixed line-end styles are handled correctly

Author: NeilMacMullen

tests/CommandLine.Tests/Fakes/HelpTextWithMixedLineBreaks_Options.cs

@@ -0,0 +1,9 @@
+namespace CommandLine.Tests.Fakes
+{
+    public class HelpTextWithMixedLineBreaks_Options
+    {
+        [Option(HelpText = 
+            "This is a help text description\n  It has multiple lines.\r\n  Third line")]
+        public string StringValue { get; set; }
+    }
+}

tests/CommandLine.Tests/Unit/Text/HelpTextTests.cs

@@ -718,5 +718,24 @@ public void HelpTextPreservesIndentationAcrossWordWrap()
         }
 
 
+        [Fact]
+        public void HelpTextIsConsitentRegardlessOfCompileTimeLineStyle()
+        {
+            // Fixture setup
+            // Exercize system 
+            var sut = new HelpText {AddDashesToOption = true}
+                .AddOptions(new NotParsed<Simple_Options>(TypeInfo.Create(typeof(HelpTextWithMixedLineBreaks_Options)),
+                    Enumerable.Empty<Error>()));
+
+            // Verify outcome
+
+            var lines = sut.ToString().ToNotEmptyLines();
+            lines[0].Should().BeEquivalentTo("  --stringvalue    This is a help text description");
+            lines[1].Should().BeEquivalentTo("                     It has multiple lines.");
+            lines[2].Should().BeEquivalentTo("                     Third line");
+         
+            // Teardown
+        }
+
     }
 }