Do something about stdin stuff for git

[zkat]

It'd be really nice if pacote were able to detect when the git subcommand was trying to prompt the user and format that in a more useful way than it does right now. It might also be necessary to have a global lock on git clones so we know only one of them is happening at a time (we don't wanna spawn more than one git child process, I think, because of conflict potential and memory use)

This might need to be done with a callback on certain kinds of output from git that npm can pass in to do things like disable the progress bar.

Or maybe even go through ASKPASS. That's probably the best answer, I think.