When subclassing `Command<TSettings>` which has the [NotNull] attributes, Rider/ReSharper gives this warning:
> Nullability of type of parameter 'context' in method does not match overridden member `int Spectre.Console.Cli.Command<TSettings>.Execute(CommandContext, TSettings)` (possibly because of nullability attributes)
When subclassing `Command<TSettings>` which does not have the [NotNull] attributes, Rider/ReSharper gives this warning:
> The nullability attribute has no effect and can be safely removed
The solution is simply to remove the [NotNull] attributes.
Since `<Nullable>enable</Nullable>` is set in the project, they are actually not necessary. By the way, the non-generic `Command` class does not have the [NotNull] attributes.
When a conversion to an enum fails, list all the valid enum values in the error message.
Message before this commit:
> Error: heimday is not a valid value for DayOfWeek.
Message after this commit:
> Error: Failed to convert 'heimday' to DayOfWeek. Valid values are 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'
Shows help if the default command was called without any arguments but has required arguments.
This way it does not hinder execution of a default command without any required arguments.
When called without args:
- Default command with required params -> Show help
- Default command with required params and additional commands -> Show help including additional commands
- Default command without required params -> Execute command
