lib/index.js
function initFile(file) {
  if (!file.s3) {
    file.s3 = {};
    file.s3.headers = {};
    file.s3.path = file.relative.replace(/\\/g, '/');
  }
  return file;
}
function initFile(file) {
  if (!file.s3) {
    file.s3 = {};
    file.s3.headers = {};
    file.s3.path = file.relative.replace(/\\/g, '/');
  }
  return file;
}
init file s3 hash
@param  {Vinyl} file file object

@return {Vinyl} file
@api private