Exit error code on CLI Command failure

[MGatner]

Description
Currently there is no way for a CLI command to indicate exit status to the shell. There are definitely better ways to do this, but this is an example of allowing commands to return false or a numeric code to indicate to spark that the CLI Command failed, and have spark exit appropriately for the shell.

Ref. #2163

Checklist:

• Securely signed commits
• Component(s) with PHPdocs
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[jim-parry]

It looks like this is patterned after HTTP status codes (>= 300 being bad).
Another though would be to pattern error codes after bash script codes (https://shapeshed.com/unix-exit-codes/), which could be more conventional for command line usage.

[MGatner]

@jim-parry I definitely agree but I think in order to do that we'll want a separate CLI Response class (spark uses HTTPResponse right now) and I think that will be a pretty large change with lots of repercussions. HTTP\Response->setStatusCode() doesn't just set a straight numerical so it isn't as easy as passing in a Unix code.

[jim-parry]

Makes sense ... twas just a thought :)

[MGatner]

A good thought! If the admins wink wink are okay with implementing a big change like this pre-RC1 I am glad to take a look at it, but I thought this was more likely to get something in since right now there's absolutely no way to do this.

[jim-parry]

I think that sticking to the HTTP codes is more sensible at the moment.
Down the road, it could be an idea to build a different CLI runner that was meant to play nicer with shell scripts.