grunt.js

// gruntfile dropin used to build a grunt files object with 1:1 structure
function globToMultiFiles(glob, dest, options) {
  var path = require('path');

  grunt.util = grunt.util || grunt.utils;

  dest = grunt.template.process(dest);

  options = grunt.util._.defaults(options || {}, {
    cwd: '',
    minimatch: {},
    processName: false
  });

  if (options.cwd.length > 0) {
    options.minimatch.cwd = options.cwd;
  }

  var result = {};

  var destFile;
  var srcFile;

  var fileName;
  var filePath;

  grunt.file.expandFiles(options.minimatch, glob).forEach(function(file) {
    fileName = path.basename(file);
    filePath = path.dirname(file);
    
    srcFile = path.join(options.cwd, file);

    if (options.processName && grunt.util.kindOf(options.processName) === 'function') {
      fileName = options.processName(fileName) || fileName;
    }

    destFile = path.join(dest, filePath, fileName);

    result[destFile] = srcFile;
  });

  return result;
}

...

// files in src to dest/src
globToMultiFiles('src/*', 'dest');

// files and folders in src to dest (retaining structure)
globToMultiFiles('**', 'dest', {cwd: 'src'});

// files and folders in src to dest (retaining structure)
// replace ext, example use case stylus
globToMultiFiles('**', 'dest', {
  cwd: 'src',
  processName: function(fileName) {
    fileName = fileName.replace('.styl', '.css');

    return fileName;
  }
});

...

task: {
  target: {
    files: globToMultiFiles(...)
  }
}