libgit2 is a portable, pure C implementation of the Git core methods provided as a re-entrant linkable library with a solid API, allowing you to write native speed custom Git applications in any language which supports C bindings.

More Information: https://libgit2.github.com/
Steps:

1. Launch Terminal by pressing command+space, type terminal and hit Enter key.
2. Run

   ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" < /dev/null 2> /dev/null

3. Install

   brew install libgit2

Done!