CLI: Exit status should be 1 when no/wrong arguments are passed

[jmini]

Inspired by #124

When the cli is run with wrong or no arguments, it returns the text:

Available languages (generators): [ada, ada-server, android, apache2, apex, aspnetcore, bash, clojure, cwiki, cpp-qt5, cpp-pistache-server, cpp-restbed-server, cpp-restsdk, cpp-tizen, csharp, csharp-dotnet2, csharp-nancyfx, dart, eiffel, elixir, elm, erlang-client, erlang-server, flash, scala-finch, go, go-server, groovy, kotlin, kotlin-server, haskell-http-client, haskell, java, jaxrs-cxf-client, java-inflector, java-msf4j, java-pkmst, java-play-framework, java-undertow-server, java-vertx, jaxrs-cxf, jaxrs-cxf-cdi, jaxrs-jersey, jaxrs-resteasy, jaxrs-resteasy-eap, jaxrs-spec, javascript, javascript-closure-angular, jmeter, lua, nodejs-server, objc, openapi, openapi-yaml, perl, php, php-lumen, php-slim, php-silex, php-symfony, php-ze-ph, powershell, python, python-flask, r, ruby, ruby-on-rails, ruby-sinatra, rust, rust-server, scalatra, scala-akka, scala-httpclient, scala-gatling, scala-lagom-server, scalaz, spring, dynamic-html, html, html2, swift2-deprecated, swift3, swift4, typescript-angular, typescript-angularjs, typescript-aurelia, typescript-fetch, typescript-inversify, typescript-jquery, typescript-node]

Take this bash script:

#!/bin/sh

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar
STATUS="${?}"
echo "Status: ${STATUS}"

The error status should be 1 and not 0

[jmini]

When this is implemented, the bin/run-all-petstore should use set -e (see https://stackoverflow.com/a/1379904) in order to propagate the error code back.

[jimschubert]

@jmini set -e will cause bin/run-all-petstore.sh to fail in first error. This usually isn't desirable behavior on CI.

We probably want to echo to stdout if a generator has errored, by inspection $?.

[jimschubert]

Also, looking at this a little more closely, exiting with status 1 will prevent scripts from piping Langs output to another command and parsing it. I'll look into whether the framework can define an exit code of 1 only when the commands is defaulted.

[jmini]

PRs:

• The return code is implemented as part of Cli generator name option, replaces 'language' options in CLI and Maven Plugin #57.
• Fixing bin/run-all-petstore.sh is Improve 'bin/run-all-petstore' #133.