Emit multi-line scalars in folded style by default.

YamlDotNet.Core/Emitter.cs

@@ -1468,7 +1468,7 @@ namespace YamlDotNet.Core
 
 			if (style == ScalarStyle.Any)
 			{
-				style = ScalarStyle.Plain;
+				style = scalarData.isMultiline ? ScalarStyle.Folded : ScalarStyle.Plain;
 			}
 
 			if (isCanonical)
@@ -1476,7 +1476,6 @@ namespace YamlDotNet.Core
 				style = ScalarStyle.DoubleQuoted;
 			}
 
-
 			if (isSimpleKeyContext && scalarData.isMultiline)
 			{
 				style = ScalarStyle.DoubleQuoted;

YamlDotNet.UnitTests/Core/EmitterTests.cs

@@ -199,6 +199,14 @@ namespace YamlDotNet.UnitTests
 			Assert.True(yaml.Contains("world"));
 		}
 
+		[Fact]
+		public void FoldedStyleIsSelectedWhenNewLinesAreFoundInLiteral()
+		{
+			var yaml = EmitScalar(new Scalar(null, null, "hello\nworld", ScalarStyle.Any, true, false));
+			Console.WriteLine(yaml);
+			Assert.True(yaml.Contains(">"));
+		}
+
 		[Fact]
 		public void FoldedStyleDoesNotGenerateExtraLineBreaks()
 		{