Use relative url when showing forked from

models/repo.go

 	return setting.AppSubUrl + "/" + repo.MustOwner().Name + "/" + repo.Name
 }
 
+func (repo *Repository) RepoRelLink() string {
+	return "/" + repo.MustOwner().Name + "/" + repo.Name
+}
+
+
 func (repo *Repository) ComposeCompareURL(oldCommitID, newCommitID string) string {
 	return fmt.Sprintf("%s/%s/compare/%s...%s", repo.MustOwner().Name, repo.Name, oldCommitID, newCommitID)
 }

templates/repo/header.tmpl

 						<div class="divider"> / </div>
 						<a href="{{$.RepoLink}}">{{.Name}}</a>
 						{{if .IsMirror}}<div class="fork-flag">{{$.i18n.Tr "repo.mirror_from"}} <a target="_blank" href="{{$.Mirror.Address}}">{{$.Mirror.Address}}</a></div>{{end}}
-						{{if .IsFork}}<div class="fork-flag">{{$.i18n.Tr "repo.forked_from"}} <a href="{{.BaseRepo.RepoLink}}">{{SubStr .BaseRepo.RepoLink 1 -1}}</a></div>{{end}}
+						{{if .IsFork}}<div class="fork-flag">{{$.i18n.Tr "repo.forked_from"}} <a href="{{.BaseRepo.RepoLink}}">{{SubStr .BaseRepo.RepoRelLink 1 -1}}</a></div>{{end}}
 					</div>
 
 					<div class="ui right">
 {{else}}
 	<div class="ui divider"></div>
 {{end}}
-</div>
+</div>