--help no longer displays the option argument if Option.HelpName is not set

[KalleOlaviNiemitalo]

In System.CommandLine 2.0.0-beta4.22272.1 (commit 209b724), if I set up an option like this

            this.jsonDirectoryOption = new Option<DirectoryInfo>(
                name: "--json-directory",
                description: "Writes API JSON responses to the specified directory.");
            this.jsonDirectoryOption.ExistingOnly();
            this.Add(this.jsonDirectoryOption);

then --help generated a default description for the argument of the option:

  --json-directory <json-directory>   Writes API JSON responses to the specified directory.

In System.CommandLine 2.0.0-beta4.23165.2 (commit 4d1e6ac), if I similarly set up an option

            this.jsonDirectoryOption = new Option<DirectoryInfo>("--json-directory")
            {
                Description = "Writes API JSON responses to the specified directory.",
            };
            this.jsonDirectoryOption.AcceptExistingOnly();
            this.Options.Add(this.jsonDirectoryOption);

then --help does not show that the option requires an argument:

  --json-directory                    Writes API JSON responses to the specified directory.

I can correct the --help output by setting Option.HelpName in my application, but this is quite a surprising change and should at least be documented in the upcoming release notes.

[KalleOlaviNiemitalo]

I guess this change came from #2073, but I did not test before and after.

[KalleOlaviNiemitalo]

If you don't want to repeat the name of the option, then possibly this could use Type.Name of the argument, or just "value" localized. If the application developer does not want the option argument to be displayed at all, then they can set HelpName = "" or customize the first column of the help.