feat(cli): use protractor.conf.js as a default config file if none is passed

Closes #615

Author: juliemr

lib/cli.js

@@ -31,8 +31,10 @@ process.argv.slice(2).forEach(function(arg) {
 var util = require('util');
 var path = require('path');
 var child = require('child_process');
-var argv = require('optimist').
+var fs = require('fs');
+var optimist = require('optimist').
     usage('Usage: protractor [options] [configFile]\n' +
+        'configFile defaults to protractor.conf.js\n' +
         'The [options] object will override values from the config file.\n' +
         'See the reference config for a full list of options.').
     describe('help', 'Print Protractor help menu').
@@ -62,11 +64,9 @@ var argv = require('optimist').
       if (arg._.length > 1) {
         throw 'Error: more than one config file specified';
       }
-      if (process.argv.length < 3 || arg.help) {
-        throw '';
-      }
-    }).
-    parse(args);
+    });
+
+var argv = optimist.parse(args);
 
 if (argv.version) {
   util.puts('Version ' + require(path.join(__dirname, '../package.json')).version);
@@ -114,5 +114,17 @@ if (argv.excludes) {
   argv.excludes = processFilePatterns_(argv.excludes);
 }
 
+// Use default configuration, if it exists.
+var configFile = argv._[0];
+if (!configFile) {
+  if (fs.existsSync('./protractor.conf.js')) {
+    configFile = './protractor.conf.js';
+  }
+}
+if (!configFile && args.length < 3) {
+  optimist.showHelp();
+  process.exit(1);
+}
+
 // Run the launcher
-require('./launcher').init(argv._[0], argv);
+require('./launcher').init(configFile, argv);

lib/launcher.js

@@ -53,6 +53,7 @@ var init = function(configFile, additionalConfig) {
       launcherExitCode = 0;
 
   var configParser = new ConfigParser();
+
   if (configFile) {
     configParser.addFileConfig(configFile);
   }