doing some config building with through2

gistfile1.txt

var through = require('through2')
var path = require('path')
var File = require('gulp-util').File
var yaml = require('js-yaml')

var configBuilder = function(fileName) {
  var buffer = [];
  var firstFile = null;
  return through.obj(function(file, enc, cb) {
    buffer.push(file.frontMatter);

    if (!firstFile) firstFile = file;
    cb();
  }, function() {
    if (buffer.length > 0) {
      var joinedPath = path.join(firstFile.base, fileName);
      var file = new File({
        cwd: firstFile.cwd,
        base: firstFile.base,
        path: joinedPath,
        contents: new Buffer(yaml.dump(buffer))
      });
      this.push(file);
    }
    this.emit('end');
  });
};