Install a local copy of libgit2
Install a local copy of libgit2

Pygit2 is tightly coupled with a minor version of libgit2. This
means that pygit2 can break when libgit2 is serviced via HomeBrew.
The solution is to provide a local copy of the correct libgit2 and
install it into the libexec directory.

xyziemba/homebrew-brew