The git2 crate needs cmake (it's on brew), and I had to supply the builder with OPENSSL_ROOT_DIR or it wouldn't compile libgit2 Correctly:
OPENSSL_ROOT_DIR=/usr/local/opt/openssl cargo buildnext_version # Shows current latest semver version or 0.0.1
next_version --major # Extracts latest and bumps major
next_version --minor # Extracts latest and bumps minor
next_version --patch # Extracts latest and bumps patch
next_version --patch ../foo # Specify git repo in another directory