old_contents: var gulp = require('gulp');
  var Dgeni = require('dgeni');
  var del = require('del');
  
  gulp.task('dgeni', ['clean'], function() {
    try {
      var dgeni = new Dgeni([require('./docs/dgeni-conf')]);
      return dgeni.generate();
    } catch(x) {
      console.log(x.stack);
      throw x;
    }
  });
  
  gulp.task('clean', function(done) {
    del(['./build'], done);
  });
  
  gulp.task('default', ['dgeni']);
new_contents: var gulp = require('gulp');
  var Dgeni = require('dgeni');
  var del = require('del');
  
  gulp.task('dgeni', ['clean'], function() {
    try {
      var dgeni = new Dgeni([require('./docs/dgeni-conf')]);
      return dgeni.generate();
    } catch(x) {
      console.log(x.stack);
      throw x;
    }
  });
  
  gulp.task('clean', function(done) {
    del(['./build'], done);
  });
  
  gulp.task('watch', ['default'], function() {
    return gulp.watch(['docs/**/*', 'src/**/*'], ['default']);
  });
  
  gulp.task('default', ['dgeni']);
subject: add a watch task