fix(external-plugins/cherrypicker): fix head branch format when skipFork

is enabled

Author: wuhuizuo

cmd/external-plugins/cherrypicker/server.go

@@ -567,6 +567,10 @@ func (s *Server) handle(logger logrus.FieldLogger, requester string, comment *gi
 		resp := fmt.Sprintf("failed to push cherry-picked changes in GitHub: %v", err)
 		return utilerrors.NewAggregate([]error{err, s.createComment(logger, org, repo, num, comment, resp)})
 	}
+	head := fmt.Sprintf("%s:%s", s.botUser.Login, newBranch)
+	if s.skipFork {
+		head = newBranch
+	}
 
 	// Open a PR in GitHub.
 	var cherryPickBody string
@@ -575,7 +579,6 @@ func (s *Server) handle(logger logrus.FieldLogger, requester string, comment *gi
 	} else {
 		cherryPickBody = cherrypicker.CreateCherrypickBody(num, "", releaseNoteFromParentPR(body), chainBranches)
 	}
-	head := fmt.Sprintf("%s:%s", s.botUser.Login, newBranch)
 	createdNum, err := s.ghc.CreatePullRequest(org, repo, title, cherryPickBody, head, targetBranch, true)
 	if err != nil {
 		logger.WithError(err).Warn("failed to create new pull request")