anchor.diff:            return _getCommits(remoteRef, remoteShas, sha);
   
           }, onError: (e) {
  -          // no commits to push.
  -          throw "no commits to push.";
  +          throw new GitException(GitErrorConstants.GIT_BRANCH_NOT_FOUND);
           });
         });
       });
  
positive.code:         return completer.future;
  
        }, onError: (e) {
          _nonFastForward();
        });
      }
      return getNextCommit(sha);
  
negative.code: 
  import 'config.dart';
  import 'constants.dart';
  import 'exception.dart';
  import 'fast_sha.dart';
  import 'file_operations.dart';
  import 'commands/index.dart';
  