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.
Add support for converting command parameters that doesn't have a built-in TypeConverter but has a constructor that takes a string. For CLI apps, FileInfo and DirectoryInfo will likely be the most useful ones, but there may be others.
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
* Support negative numbers as command option values
* Support command line options before arguments
* POSIX-compliant handling of quotes (double and single, terminated and unterminated), whitespace, hyphens, and special characters (e.g. emojis)
