Add configuration setting to put cf push in verbose mode

[mikegehard]

For debugging purposes, it would be nice to be able to set CF_TRACE=true when running this resource. I had a problem with an extra / at the end of an API endpoint that caused the CF CLI to fail with an "Unknown command" error that didn't tell me much about what is wrong.

I propose adding a configuration setting debug, that defaults to false, to help with this.

[JohannesRudolph]

I've had a go at this, since we also found the need for this setting: https://github.com/meshcloud/cf-resource/tree/feature/support-verbose

However, with my changes put steps on the modified cf-resource would ocassionally fail with an error message like this:

REQUEST: [2018-02-06T09:47:52Z]
GET /v2/apps?q=name:panel&q=space_guid:76ab50b9-0d34-47a0-8279-b1d4691de6a8 HTTP/1.1
Host: api.cf.dev.eu-de-central.msh.host
Accept: application/json
Authorization: [PRIVATE DATA HIDDEN]
Connection: close
Content-Type: application/json
User-Agent: go-cli 6.34.1+bbdf81482.2018-01-17 / linux

RESPONSE: [2018-02-06T09:47:52Z]
HTTP/1.1 200 OK
Connection: close
Content-Length: 3361
Content-Type: application/json;charset=utf-8
Date: Tue, 06 Feb 2018 09:47:52 GMT
Server: nginx
X-Content-Type-Options: nosniff
X-Vcap-Request-Id: aa1681f5-7a54-4fdf-4528-5911cb162b59::521c3723-7431-45ce-9081-d0e420899095

{
...
}
error: unexpected end of JSON input
error running command: exit status 1

I'm not sure why this happens, as the cf cli output is explicitly redirected to stderr so that it doesn't trip up concourse:

func (cf *CloudFoundry) cf(args ...string) *exec.Cmd {
	cmd := exec.Command("cf", args...)
	cmd.Stdout = os.Stderr
	cmd.Stderr = os.Stderr
	cmd.Env = append(os.Environ(), "CF_COLOR=true", "CF_DIAL_TIMEOUT=30")

	if cf.verbose {
		cmd.Env = append(cmd.Env, "CF_TRACE=true")
	}

	return cmd
}

Any ideas?

[JohannesRudolph]

Appears to be related to a known issue in the cf cli.

API tracing to terminal (using CF_TRACE=true, -v option or cf config --trace) doesn't work well with some CLI plugin commands. Trace to file works fine. On Linux, CF_TRACE=/dev/stdout works too.

I'll try fixing it by setting CF_TRACE=/dev/stderr

via cloudfoundry-attic/Diego-Enabler#6