https://android.googlesource.com/
https://github.com/aosp-mirror  github上那个重要仓库的汇集地址
https://github.com/foxleezh/AOSP/issues/1 如何下载Android源码
https://source.android.google.cn/devices/tech/ota/ab

https://github.com/Joyounger/update_engine.git
https://aosp.tuna.tsinghua.edu.cn/platform/system/update_engine.git
git clone https://aosp.tuna.tsinghua.edu.cn/platform/system/update_engine