Export a tree externally while passing it through.

broccoli-tee-tree.js

var rimraf   = require('rimraf');
var helpers  = require('broccoli-kitchen-sink-helpers');

function TeeTree(inputTree, otherDir) {
  this.inputTree = inputTree;
  this.otherDir = otherDir;
}

TeeTree.prototype.read = function (readTree) {
  var otherDir = this.otherDir;
  return readTree(this.inputTree).then(function (srcDir) {
    rimraf.sync(otherDir);
    helpers.copyRecursivelySync(srcDir, otherDir);
    return srcDir; // passthrough
  });
};

TeeTree.prototype.cleanup = function () {};

module.exports = TeeTree;