CLI option for help/documentation does not work as described

Description

Following the README I tried to get documentation for the generate command with:

java -jar swagger-codegen-cli-3.0.35.jar help generate

The output is not the documentation, but this:

usage: swagger-codegen [-h] Command ...

named arguments:
  -h, --help             show this help message and exit

commands:
  Command                additional help
    generate             generate
    config-help          config-help
    meta                 meta
    langs                langs
    version              version

Swagger-codegen version

The latest from Maven Central, 3.0.35.

Swagger declaration file content or url

None

Command line used for generation

java -jar swagger-codegen-cli-3.0.35.jar help generate

Also tried

java -jar swagger-codegen-cli-3.0.35.jar -h generate
java -jar swagger-codegen-cli-3.0.35.jar --help generate

with the same result.

This suggestion:

java -jar swagger-codegen-cli-3.0.35.jar config-help

Crashes the program with:

Exception in thread "Thread-0" java.lang.NullPointerException
        at java.base/java.lang.String.concat(Unknown Source)
        at io.swagger.codegen.v3.CodegenConfigLoader.forName(CodegenConfigLoader.java:31)
        at io.swagger.codegen.v3.cli.cmd.ConfigHelp.run(ConfigHelp.java:17)
        at java.base/java.lang.Thread.run(Unknown Source)

Steps to reproduce

See description above.

Related issues/PRs

Suggest a fix/enhancement

Do not hide the documentation in the command, but include it this repo and link from the README.

Start with the README command examples and the stack-trace locations in CodegenConfigLoader.java and ConfigHelp.java. Reproduce the documented help and config-help commands, then verify that the CLI returns the expected documentation without crashing.