FIX 解决头歌版本库无法访问的问题

app/views/repositories/detail.json.jbuilder

@@ -48,7 +48,7 @@ if @result[:repo]
   json.size replace_bytes_to_b(number_to_human_size(@result[:repo]['size'].to_i*1024))
   json.ssh_url @result[:repo]['ssh_url']
   json.clone_url @result[:repo]['clone_url']
-  json.default_branch @result[:repo]['default_branch']
+  json.default_branch @project.educoder? ? "master" : @result[:repo]['default_branch']
   json.empty @result[:repo]['empty']
   json.full_name @result[:repo]['full_name']
   json.private @result[:repo]['private']