default RootCommand.HelpName from ToolCommandName build property

Author: jonsequitur

src/System.CommandLine/System.CommandLine.csproj

@@ -19,6 +19,7 @@
   <ItemGroup>
     <Compile Include="..\System.Diagnostics.CodeAnalysis.cs" Link="System.Diagnostics.CodeAnalysis\System.Diagnostics.CodeAnalysis.cs" />
     <None Include="README.md" Pack="true" PackagePath="/README.md" />
+    <None Include="buildTransitive\**" Pack="true" PackagePath="buildTransitive\" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">

src/System.CommandLine/buildTransitive/System.CommandLine.targets

@@ -0,0 +1,10 @@
+<Project>
+
+  <ItemGroup Condition="'$(ToolCommandName)' != ''">
+    <AssemblyAttribute Include="System.Reflection.AssemblyMetadataAttribute">
+      <_Parameter1>System.CommandLine.ToolCommandName</_Parameter1>
+      <_Parameter2>$(ToolCommandName)</_Parameter2>
+    </AssemblyAttribute>
+  </ItemGroup>
+
+</Project>