libgit2

Portable, pure C implementation of the Git core

libgit2 is... licensed under a very permissive license so you can use it anywhere faster than any other Git library written in standards compliant C99 completely multi-platform: Windows, Linux, Mac OS X, xBSD compiled natively under all platforms (yes, even MSVC on Windows) re-entrant, with sane error handling designed with a solid and consistent API available as bindings for all major scripting languages