Allow custom help providers (#1259)

Allow custom help providers

* Version option will show in help even with a default command

* Reserve `-v` and `--version` as special Spectre.Console command line arguments (nb. breaking change for Spectre.Console users who have a default command with a settings class that uses either of these switches).

* Help writer correctly determines if trailing commands exist and whether to display them as optional or mandatory in the usage statement.

* Ability to control the number of indirect commands to display in the help text when the command itself doesn't have any examples of its own. Defaults to 5 (for backward compatibility) but can be set to any integer or zero to disable completely.

* Significant increase in unit test coverage for the help writer.

* Minor grammatical improvements to website documentation.

examples/Cli/Demo/Program.cs

@@ -15,25 +15,25 @@ public static class Program
         {
             config.SetApplicationName("fake-dotnet");
             config.ValidateExamples();
-            config.AddExample(new[] { "run", "--no-build" });
-
-                // Run
-                config.AddCommand<RunCommand>("run");
-
-                // Add
-                config.AddBranch<AddSettings>("add", add =>
-            {
-                add.SetDescription("Add a package or reference to a .NET project");
-                add.AddCommand<AddPackageCommand>("package");
-                add.AddCommand<AddReferenceCommand>("reference");
+            config.AddExample("run", "--no-build");
+
+            // Run
+            config.AddCommand<RunCommand>("run");
+
+            // Add
+            config.AddBranch<AddSettings>("add", add =>
+            {
+                add.SetDescription("Add a package or reference to a .NET project");
+                add.AddCommand<AddPackageCommand>("package");
+                add.AddCommand<AddReferenceCommand>("reference");
+            });
+
+            // Serve
+            config.AddCommand<ServeCommand>("serve")
+                .WithExample("serve", "-o", "firefox")
+                .WithExample("serve", "--port", "80", "-o", "firefox");
             });
 
-                // Serve
-                config.AddCommand<ServeCommand>("serve")
-                .WithExample(new[] { "serve", "-o", "firefox" })
-                .WithExample(new[] { "serve", "--port", "80", "-o", "firefox" });
-        });
-
         return app.Run(args);
     }
 }

examples/Cli/Help/CustomHelpProvider.cs

@@ -0,0 +1,30 @@
+using System.Linq;
+using Spectre.Console;
+using Spectre.Console.Cli;
+using Spectre.Console.Cli.Help;
+using Spectre.Console.Rendering;
+
+namespace Help;
+
+/// <summary>
+/// Example showing how to extend the built-in Spectre.Console help provider
+/// by rendering a custom banner at the top of the help information
+/// </summary>
+internal class CustomHelpProvider : HelpProvider
+{
+    public CustomHelpProvider(ICommandAppSettings settings)
+        : base(settings)
+    {
+    }
+
+    public override IEnumerable<IRenderable> GetHeader(ICommandModel model, ICommandInfo? command)
+    {
+        return new[]
+        {
+            new Text("--------------------------------------"), Text.NewLine,
+            new Text("---      CUSTOM HELP PROVIDER      ---"), Text.NewLine,
+            new Text("--------------------------------------"), Text.NewLine,
+            Text.NewLine,
+        };
+    }
+}

examples/Cli/Help/DefaultCommand.cs

@@ -0,0 +1,20 @@
+using Spectre.Console;
+using Spectre.Console.Cli;
+
+namespace Help;
+
+public sealed class DefaultCommand : Command
+{
+    private IAnsiConsole _console;
+
+    public DefaultCommand(IAnsiConsole console)
+    {
+        _console = console;
+    }
+
+    public override int Execute(CommandContext context)
+    {
+        _console.WriteLine("Hello world");
+        return 0;
+    }
+}

examples/Cli/Help/Help.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <ExampleName>Help</ExampleName>
+    <ExampleDescription>Demonstrates how to extend the built-in Spectre.Console help provider to render a custom banner at the top of the help information.</ExampleDescription>
+    <ExampleGroup>Cli</ExampleGroup>
+    <ExampleVisible>false</ExampleVisible>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\Shared\Shared.csproj" />
+  </ItemGroup>
+
+</Project>

examples/Cli/Help/Program.cs

@@ -0,0 +1,19 @@
+using Spectre.Console.Cli;
+
+namespace Help;
+
+public static class Program
+{
+    public static int Main(string[] args)
+    {
+        var app = new CommandApp<DefaultCommand>();
+
+        app.Configure(config =>
+        {
+            // Register the custom help provider
+            config.SetHelpProvider(new CustomHelpProvider(config.Settings));
+        });
+
+        return app.Run(args);
+    }
+}