Oto README i przykłady:https://github.com/gruntjs/grunt-contrib-copy/blob/master/README.md.Oto odpowiednia część kodu (której najwyraźniej nie mogę zrozumieć)https://github.com/gruntjs/grunt-contrib-copy/blob/master/tasks/copy.js:

module.exports = function(grunt) {
  'use strict';

  var path = require('path');

  grunt.registerMultiTask('copy', 'Copy files.', function() {
    var kindOf = grunt.util.kindOf;

    var options = this.options({
      processContent: false,
      processContentExclude: []
    });

    var copyOptions = {
      process: options.processContent,
      noProcess: options.processContentExclude
    };

    grunt.verbose.writeflags(options, 'Options');

    var dest;
    var isExpandedPair;
    var tally = {
      dirs: 0,
      files: 0
    };

    this.files.forEach(function(filePair) {
      isExpandedPair = filePair.orig.expand || false;

      filePair.src.forEach(function(src) {
        if (detectDestType(filePair.dest) === 'directory') {
          dest = (isExpandedPair) ? filePair.dest : unixifyPath(path.join(filePair.dest, src));
        } else {
          dest = filePair.dest;
        }

        if (grunt.file.isDir(src)) {
          grunt.verbose.writeln('Creating ' + dest.cyan);
          grunt.file.mkdir(dest);
          tally.dirs++;
        } else {
          grunt.verbose.writeln('Copying ' + src.cyan + ' -> ' + dest.cyan);
          grunt.file.copy(src, dest, copyOptions);
          tally.files++;
        }
      });
    });