setupMirrorFromCache() {
    var _this = this;

    return (0, (_asyncToGenerator2 || _load_asyncToGenerator()).default)(function* () {
      const tarballMirrorPath = _this.getTarballMirrorPath();
      const tarballCachePath = _this.getTarballCachePath();

      if (tarballMirrorPath == null) {
        return;
      }

      if (!(yield (_fs || _load_fs()).exists(tarballMirrorPath)) && (yield (_fs || _load_fs()).exists(tarballCachePath))) {
        // The tarball doesn't exists in the offline cache but does in the cache; we import it to the mirror
        yield (_fs || _load_fs()).mkdirp(path.dirname(tarballMirrorPath));
        yield (_fs || _load_fs()).copy(tarballCachePath, tarballMirrorPath, _this.reporter);
      }
    })();
  }
Given a list of patterns, dedupe them to a list of unique patterns.