repo/git/gerrit

https://source.android.com/source/developing.html
https://source.android.com/source/using-repo.html
https://source.android.com/source/submit-patches.html
https://gerrit.googlecode.com/svn/documentation/2.2.1/user-upload.html
https://git.eclipse.org/r/Documentation/user-changeid.html
http://xda-university.com/as-a-developer/repo-tips-tricks
https://kobablog.wordpress.com/2011/05/12/tips-of-repo-sync-of-android/

[Note] repo init --referenece...
[Note] git checkout FETCH_HEAD , escape from branch...