Not to veer too far from the main discussion, but 'git' isn't just some giant monolithic binary. The 'git' command is a wrapper around a bunch of different, relatively modular binaries. They each even have their own man page. (e.g. 'git push' maps to 'git-push'). Each is just a unique action that can be applied to a common data structure (the git repository).
Do an ls /usr/libexec/git-core/ (or your operating system's equivalent) some time. The fact that the porcelain exists does not mean that the plumbing does not.
Look closer at git, and you'll see that it's actually a collection of smaller programs (each of the git commands is made as a separate executable before being combined into git)