Added the ability to hide CommandOptions. (#642)

CommandOptions now has an IsHidden property that, when set to true, will cause the option to be hidden from the following cases:

- Help text using `-h|--help`
- Xml representations generated with the `cli xml` command
- Diagnostics displayed with the `cli explain` command

Hidden options can still be outputted with `cli explain` using the `--hidden` option that is also used to display hidden commands.

Fixes #631

src/Spectre.Console/Cli/Annotations/CommandOptionAttribute.cs

@@ -34,6 +34,11 @@ namespace Spectre.Console.Cli
         /// </summary>
         public bool ValueIsOptional { get; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether this option is hidden from the help text.
+        /// </summary>
+        public bool IsHidden { get; set; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="CommandOptionAttribute"/> class.
         /// </summary>

src/Spectre.Console/Cli/Internal/Commands/ExplainCommand.cs

@@ -36,7 +36,7 @@ namespace Spectre.Console.Cli
             [CommandOption("-d|--detailed")]
             public bool? Detailed { get; }
 
-            [Description("Include hidden commands.")]
+            [Description("Include hidden commands and options.")]
             [CommandOption("--hidden")]
             public bool IncludeHidden { get; }
         }
@@ -166,7 +166,7 @@ namespace Spectre.Console.Cli
                     var parametersNode = commandNode.AddNode(ParentMarkup("Parameters"));
                     foreach (var parameter in command.Parameters)
                     {
-                        AddParameter(parametersNode, parameter, detailed);
+                        AddParameter(parametersNode, parameter, detailed, includeHidden);
                     }
                 }
 
@@ -181,8 +181,13 @@ namespace Spectre.Console.Cli
             }
         }
 
-        private void AddParameter(TreeNode parametersNode, CommandParameter parameter, bool detailed)
+        private void AddParameter(TreeNode parametersNode, CommandParameter parameter, bool detailed, bool includeHidden)
         {
+            if (!includeHidden && parameter.IsHidden)
+            {
+                return;
+            }
+
             if (!detailed)
             {
                 parametersNode.AddNode(

src/Spectre.Console/Cli/Internal/Commands/XmlDocCommand.cs

@@ -153,6 +153,7 @@ namespace Spectre.Console.Cli
 
             // Options
             foreach (var option in command.Parameters.OfType<CommandOption>()
+                .Where(x => !x.IsHidden)
                 .OrderBy(x => string.Join(",", x.LongNames))
                 .ThenBy(x => string.Join(",", x.ShortNames)))
             {

src/Spectre.Console/Cli/Internal/HelpWriter.cs

@@ -61,7 +61,7 @@ namespace Spectre.Console.Cli
                     parameters.Add(new HelpOption("v", "version", null, null, "Prints version information"));
                 }
 
-                parameters.AddRange(command?.Parameters?.OfType<CommandOption>()?.Select(o =>
+                parameters.AddRange(command?.Parameters.OfType<CommandOption>().Where(o => !o.IsHidden).Select(o =>
                     new HelpOption(
                         o.ShortNames.FirstOrDefault(), o.LongNames.FirstOrDefault(),
                         o.ValueName, o.ValueIsOptional, o.Description))

src/Spectre.Console/Cli/Internal/Modelling/CommandArgument.cs

@@ -16,7 +16,7 @@ namespace Spectre.Console.Cli
             CommandArgumentAttribute argument, ParameterValueProviderAttribute? valueProvider,
             IEnumerable<ParameterValidationAttribute> validators)
                 : base(parameterType, parameterKind, property, description, converter, defaultValue,
-                      null, valueProvider, validators, argument.IsRequired)
+                      null, valueProvider, validators, argument.IsRequired, false)
         {
             Value = argument.ValueName;
             Position = argument.Position;

src/Spectre.Console/Cli/Internal/Modelling/CommandOption.cs

@@ -20,7 +20,7 @@ namespace Spectre.Console.Cli
             IEnumerable<ParameterValidationAttribute> validators,
             DefaultValueAttribute? defaultValue, bool valueIsOptional)
                 : base(parameterType, parameterKind, property, description, converter,
-                      defaultValue, deconstructor, valueProvider, validators, false)
+                      defaultValue, deconstructor, valueProvider, validators, false, optionAttribute.IsHidden)
         {
             LongNames = optionAttribute.LongNames;
             ShortNames = optionAttribute.ShortNames;

src/Spectre.Console/Cli/Internal/Modelling/CommandParameter.cs

@@ -19,6 +19,7 @@ namespace Spectre.Console.Cli
         public List<ParameterValidationAttribute> Validators { get; }
         public ParameterValueProviderAttribute? ValueProvider { get; }
         public bool Required { get; set; }
+        public bool IsHidden { get; }
         public string PropertyName => Property.Name;
 
         public virtual bool WantRawValue => ParameterType.IsPairDeconstructable()
@@ -30,7 +31,7 @@ namespace Spectre.Console.Cli
             DefaultValueAttribute? defaultValue,
             PairDeconstructorAttribute? deconstructor,
             ParameterValueProviderAttribute? valueProvider,
-            IEnumerable<ParameterValidationAttribute> validators, bool required)
+            IEnumerable<ParameterValidationAttribute> validators, bool required, bool isHidden)
         {
             Id = Guid.NewGuid();
             ParameterType = parameterType;
@@ -43,6 +44,7 @@ namespace Spectre.Console.Cli
             ValueProvider = valueProvider;
             Validators = new List<ParameterValidationAttribute>(validators ?? Array.Empty<ParameterValidationAttribute>());
             Required = required;
+            IsHidden = isHidden;
         }
 
         public bool IsFlagValue()