YamlDotNet update to v8.0.0

Author: arturcic

src/Directory.Build.props

@@ -17,7 +17,7 @@
     <PackageVersion_LibGit2Sharp>0.26.1</PackageVersion_LibGit2Sharp>
     <PackageVersion_LibGit2Sharp_NativeBinaries>2.0.289</PackageVersion_LibGit2Sharp_NativeBinaries>
     <PackageVersion_JetBrainsAnnotations>2019.1.3</PackageVersion_JetBrainsAnnotations>
-    <PackageVersion_YamlDotNet>7.0.0</PackageVersion_YamlDotNet>
+    <PackageVersion_YamlDotNet>8.0.0</PackageVersion_YamlDotNet>
     <PackageVersion_NewtonsoftJson>12.0.2</PackageVersion_NewtonsoftJson>
 
     <PackageVersion_MicrosoftTestSdk>16.3.0</PackageVersion_MicrosoftTestSdk>

src/GitVersionCore/Configuration/ConfigSerialiser.cs

@@ -19,7 +19,7 @@ public static Config Read(TextReader reader)
 
         public static void Write(Config config, TextWriter writer)
         {
-            var serializer = new SerializerBuilder().WithNamingConvention(HyphenatedNamingConvention.Instance).Build();
+            var serializer = new SerializerBuilder().ConfigureDefaultValuesHandling(DefaultValuesHandling.OmitDefaults).WithNamingConvention(HyphenatedNamingConvention.Instance).Build();
             serializer.Serialize(writer, config);
         }
     }