Restify.plugins.serverStatic option "appendRequestPath" is bugged

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Bug Report

Restify.plugins.serverStatic option "appendRequestPath" is not working properly.

Restify Version

v6.3.4

Node.js Version

v8.91

Expected behaviour

I expected appendRequestPath = false; to make it so that the request path is not appended to the file path. (As stated in the documentation at http://restify.com/docs/plugins-api/#servestatic)

Actual behaviour

The request path was appended to the file path, despite the fact that appendRequestPath was set to false.

Repro case

index.js

var restify = require('restify');

const server = restify.createServer({
    name: 'myapp',
    version: '1.0.0'
  });

server.get('/endpoint', restify.plugins.serveStatic({
    directory: __dirname, // dirname is /Users/keithlee96/testFolder/test-api
    default: 'index.html',
    appendRequestPath: false
}));

server.listen(9090, function(){
    console.log('%s listening at %s', server.name, server.url);
});

index.html was in the same folder.

I ran the file with node index.js
When I made a get request to localhost:9090/endpoint in postman, I got the error:

{
    "code": "ResourceNotFound",
    "message": "/endpoint; caused by Error: ENOENT: no such file or directory, stat '/Users/keithlee96/testFolder/test-api/endpoint'"
}

Expected the targeted file path to be: '/Users/keithlee96/testFolder/test-api/index.html'

Are you willing and able to fix this?

No, I'm no familiar with typescript, so I don't know how to fix the error myself. I just want it to behave as the documentation http://restify.com/docs/plugins-api/#servestatic says it should. Any help on this would be greatly appreciated.

The reproduction is in index.js and uses restify.plugins.serveStatic with appendRequestPath set to false; start by locating the serveStatic implementation and reproducing the request to /endpoint. Done means the option prevents /endpoint from being appended and resolves index.html as described in the issue.