title: gulp - passing args to tasks called in the runSequence
body: <p>I have a gulp task configured like so:</p>
  
  <pre><code>gulp.task('concatenate_client_js', function(){
    return merge2(
        gulp.src('./gulp/buildConfig.json')
          .pipe(plugins.ngConfig('app.envConfig', {
            environment: 'development'
          })
        ),
        gulp.src(paths.clientJS)
      )
      .pipe(plugins.concat('angular_app.js'))
      .pipe(gulp.dest(paths.distScripts));
  });
  </code></pre>
  
  <p>This task is then called in the runSequence of other tasks (split across different gulp files) I have like so:</p>
  
  <pre><code>gulp.task('prepare-dev-files', function(callback){
    runSequence('clean_dist_dir', 'copy_assets', 'copy_serverFiles', 'copy_bower_css',
    ['compile_bower_sass', 'concatonate_bower_js'],
    'compile_sass', 'concatenate_client_js', 'compile_main_js', callback);
  });
  
  gulp.task('prepare-staging-files',  ['prepare-dev-files'], function(callback) {
    runSequence('clean_test_src', 'copy_unitTestFiles', 'copy_files_for_coverage_report', 'karma_tests_ci', callback)
  });
  </code></pre>
  
  <p>What I would like to be able to do is to set the <code>environment</code>config option to the <code>ngConfig</code> plugin in the <code>concatenate_client_js</code> task based on args or params supplied to the task.</p>
  
  <p>I have seen tools like yargs but am unsure how to use in my case. I would like to be able to supply an arg e.g <code>--mode development</code> to the call to my task in the runSequence's, e.g.</p>
  
  <pre><code>gulp.task('prepare-staging-files',  ['prepare-dev-files --mode staging'], function(callback) {
        runSequence('clean_test_src', 'copy_unitTestFiles', 'copy_files_for_coverage_report', 'karma_tests_ci', callback)
      });
  </code></pre>
  
  <p>And then add some switch code based on the mode argument passed to the task.</p>
  
  <p>Is this achievable?
  Thanks</p>