Cannot fetch a remote which URL is relative

I'm using submodules where the origin is specified as a relative URL (like ../../../modules/ModuleA). When trying to fetch from this remote, it fails with Unsupported URL protocol when calling Proxy.git_remote_connect(remoteHandle, GitDirection.Fetch);

I think a fix could be to make the URL absolute based on the repository URL.

從 Proxy.git_remote_connect(remoteHandle, GitDirection.Fetch) 開始，目前相對 submodule remote 會在此產生不支援的 URL 協定錯誤。追蹤此呼叫之前 repository URL 和 remote URL 的處理方式。完成條件是：從相對 submodule origin fetch 時，能夠以 repository URL 為基準解析它，同時不破壞絕對 remote。