Grunt 0.4.0a (devel) Run a subproject's grunt tasks.

grunt-subgrunt.js

/*
 * grunt-subgrunt
 * http://gruntjs.com/
 *
 * Copyright (c) 2012 "Cowboy" Ben Alman
 * Licensed under the MIT license.
 * https://github.com/gruntjs/grunt/blob/master/LICENSE-MIT
 */

'use strict';

module.exports = function(grunt) {

  // Nodejs libs.
  var path = require('path');

  grunt.registerMultiTask('subgrunt', 'Run a sub-project\'s grunt tasks.', function() {
    if (!grunt.file.exists(this.data.subdir)) {
      grunt.log.error('Directory "' + this.data.subdir + '" not found.');
      return false;
    }
    var done = this.async();
    var subdir = path.resolve(this.data.subdir);
    grunt.util.spawn({
      cmd: path.join(subdir, 'node_modules/.bin/grunt'),
      args: this.data.args || [],
      opts: {cwd: subdir},
    }, function(error, result, code) {
      if (code === 127) {
        grunt.log.error('Error running sub-grunt. Did you run "npm install" in the sub-project?');
      } else {
        grunt.log.writeln('\n' + result.stdout);
      }
      done(code === 0);
    });
  });

};

usage.js

// Project configuration.
grunt.initConfig({
  subgrunt: {
    foo: {
      subdir: './foo/',
      args: ['jshint', 'qunit'],
    },
  },
});

In this example, grunt subgrunt:foo would run grunt in the foo subdirectory.

Assuming that npm install had been run in there first :)

(Note: untested in Windows)