Added help informaton about config overriding

bin/docpub.js

@@ -18,6 +18,25 @@ program
     .option('--config-path <configPath>', 'path for the config')
     .option('-v --verbose', 'verbose output');
 
+program.on('--help', () => {
+    console.log('  Overriding config');
+    console.log('    To override any config option use full option path converted to --kebab-case');
+    console.log('');
+
+    console.log('    Examples:');
+    console.log('      docpub --username user@example.com');
+    console.log('      docpub --token abcdefghijklmn12345');
+    console.log('');
+    console.log('    You can also use environment variables converted to snake_case with');
+    console.log('    docpub_ prefix');
+    console.log('');
+    console.log('    Examples:');
+    console.log('      docpub_url=my-awesome-docs.zendesk.com docpub');
+    console.log('      docpub_token=abcdefghijklmn12345 docpub');
+    console.log('');
+    console.log('    If both cli flag and env var are used, cli flag takes precedence') ;
+});
+
 program.parse(process.argv);
 
 const docpub = new Docpub(program);