How can I perform an asynchronous operation before grunt.initConfig()?

Now I have my Gruntfile setup to perform some automatic detection magic like parsing sourcefiles to parse some PHP sources in roder to dynamically figure out filenames and paths I need to know before running grunt.initConfig().

Unfortunately grunt.initConfig() doesn't seem to be meant to be run asynchronously, so I see no way to have my asynchronous code executed before I can call it. Is there a trick to accomplish this or do I have to rewrite my detection routines synchronously? Is there any easy way to block execution before my callback has arrived?

Inside grunt tasks there is of course this.async(), but for initConfig() that doesn't work.

Here's a stripped down example:

function findSomeFilesAndPaths(callback) {
  // async tasks that detect and parse
  // and execute callback(results) when done
}

module.exports = function (grunt) {
  var config = {
    pkg: grunt.file.readJSON('package.json'),
  }

  findSomeFilesAndPaths(function (results) {
    config.watch = {
      coffee: {
        files: results.coffeeDir + "**/*.coffee",
        tasks: ["coffee"]
         // ...
      }
    };

    grunt.initConfig(config);

    grunt.loadNpmTasks "grunt-contrib-coffee"
    // grunt.loadNpmTasks(...);
  });
};

Any good ideas how to get this done?

Thanks a lot!