[recursive]

To me, that ought to be a concern of the "porcelain", although no one uses that word anymore. CLI is particularly bad at certain types of interaction. So to compensate, a mitigation is moved into the underlying model of git. That mitigation is staging. The inconvenience of "piecemeal adding" could have easily been addressed in the UI layer using a more suitable presentation, rather than forcing all clients to follow the stage/commit dichotomy.