[Development] atomic commits across submodules

[Oswald Buddenhagen]

On Mon, Dec 18, 2017 at 09:22:31AM -0500, Adam Treat wrote:
> 3) Private API being changed out from under
>
3a) yet unreleased public api being revised.

there is just no reasonable way to claim that the pain inflicted by the
5-stage workaround is a good thing. it's a barely acceptable thing given
the constraint of atomic commits being unrealistic for the time being.