ubuntu20.4下载Android源码，使用清华的每日更新包，步骤如下：
sudo apt install curl python git git-lfs
解压清华每月更新包
repo forall -c git reset --hard
删除目录 .repo/manifests
使用Github 镜像
repo init -u https://hub.fastgit.org/khadas/android_manifest.git -b khadas-vims-pie
修改default.xml 使用国内镜像源：
victorf@ubuntu:~/khadas/aosp/.repo/manifests$ git diff
diff --git a/default.xml b/default.xml
index 1f50e76b4…f6bf7c8fe 100644
— a/default.xml
+++ b/default.xml
@@ -1,7 +1,7 @@
同步：
export REPO_URL=‘https://mirrors.tuna.tsinghua.edu.cn/git/git-repo’
repo sync --force-sync -j4
最后出下面的错误，无法进行下一步repo start：
victorf@ubuntu:~/khadas/aosp$ repo sync -j4
Fetching: 100% (695/695), done in 18.522s
Garbage collecting: 100% (695/695), done in 2.019s
info: A new version of repo is available
warning: repo is not tracking a remote branch, so it will not receive updates
repo reset: error: Entry ‘completion.bash’ not uptodate. Cannot merge.
fatal: Could not reset index file to revision ‘v2.16.4^0’.