anchor.diff:  import 'fetch.dart';
   import '../exception.dart';
   import '../objectstore.dart';
  -import '../exception.dart';
   import '../options.dart';
   
   /**
  
positive.code:    * 6) cannot end with '.lock'.
    */
    static const BRANCH_PATTERN
        = r"^(?!/|.*([/.]\\.|//|@\\{|\\\\))[^\\x00-\\x20 ~^:?*\\[]+$";
  
    static final branchRegex = new RegExp(BRANCH_PATTERN);
  
  
negative.code:     if (remoteBranchName != null && remoteBranchName.isNotEmpty) {
        return options.store.getRemoteHeadForRef(remoteBranchName).then((sha) {
          options.depth = 1;
          options.branchName = remoteBranchName;
          Fetch fetch = new Fetch(options);
  
          Function createBranch = () {
            options.branchName = branchName;
            return store.createNewRef('refs/heads/' + branchName, sha);
          };
  
          return fetch.fetch().then((_) {
            return createBranch();
          }, onError: (GitException e) {
            if (e is! GitException ||
                e.errorCode != GitErrorConstants.GIT_FETCH_UP_TO_DATE) {
              throw e;
            }
            return createBranch();
          });
        });
      } else {
  