fix: use correct flag in dockerfile (#18)

Update the Dockerfile entrypoint script to use the correct version flag
syntax. The flag now requires two dashes instead of one. The syntax for
the texfile collector has also change, and the script was updated
accordingly.
Fix incorrect order of variable assignment when parsing CLI flags.

src/cfg/cfg.go

@@ -81,6 +81,8 @@ func readParamsFromCli(settings *AppSettings) {
 		Envar(basicAuthPassEnvName).
 		String()
 
+	kingpin.Parse()
+
 	settings.VersionMode = *versionMode
 	settings.MetricsPort = *port
 	settings.MetricsAddress = *address
@@ -88,8 +90,6 @@ func readParamsFromCli(settings *AppSettings) {
 	settings.FileCollectorEnabled = *fileCollectorEnabled
 	settings.FileCollectorPath = *fileCollectorPath
 	settings.setBasicAuthValues(*rawBasicAuthUsername, *rawBasicAuthPassword)
-
-	kingpin.Parse()
 }
 
 func (settings *AppSettings) setBasicAuthValues(rawUsername, rawPassword string) {