>FWIW, I found `git subtree` highly confusing, and hated using it. If you
>intend to maintain your package repository both in ELPA and somewhere
>else concurrently, I've found doing an "external" to be much easier to
>handle.
As a new contributer, I do not fimilar two external-method, the reason I choice subtree is that README say: If you don't know how to choice, use subtree :-)