code: function(filepath, options) {
          // options.mtimeOffset: 3 default
          if (!fileUpdates.offset) { fileUpdates.offset = options.mtimeOffset || 3; }
          if (!fileUpdates.storeData) {
            // Initialize data.
            if (grunt.file.exists(fileUpdates.storeDataPath)) {
              fileUpdates.storeData = grunt.file.readJSON(fileUpdates.storeDataPath);
            }
            if (!fileUpdates.storeData) { fileUpdates.storeData = {}; }
            // Run the task that finalize data.
            grunt.task.run('taskHelperFin');
            // The task starts after current target. NOT task.
            // (i.e. every target, and before other tasks)
            // Can't specify time after all tasks?
            // Grunt 0.5 may support a event that all tasks finish.
            // https://github.com/gruntjs/grunt/wiki/Roadmap
          }
  
          filepath = path.resolve(filepath); // full-path
          if (!(filepath in fileUpdates.storeData)) { fileUpdates.storeData[filepath] = 0; }
          return fileUpdates.storeData[filepath];
        }
docs: retrieve last update of file.