libgit2

[tanvirtin]

Research introduction of libgit2. We cannot do 1 to 1 mapping however we can partially replace frequent hitting commands with libgit2 counterparts to prevent spawning new processes.

Users should be allowed to opt in. The API should be a 1 to 1 mapping, opting in would require the path to the .dylib file that the user has to provide.

libgit2 should only be considered if it does provide an optimization to existing plumbing.