This project contains only the cpp/src files from upstream.  To update:
git merge aosp/upstream-master
If upstream has changes outside the cpp/src directory (likely), it will get
conflicts on the modified files.  To drop the changes to the unmerged
directories:
git rm -rf data
git rm -rf java
git rm -rf cpp/data
git rm -rf cpp/ext
git rm -rf cpp/tools
git commit