The latest release of libgit2/libgit2 is v1.9.7. This project is a portable, linkable library that implements the core features of Git in pure C. It is linked into applications to provide APIs for working with repository management, commits, trees, references, the index, and configuration. However, the provided information does not describe anything newly added or changed in v1.9.7, so the specific changes in this version cannot be confirmed.
What libgit2 aims at is not building the Git command-line tool itself, but integrating version control features into other applications. It can be used in services and apps that need to handle repositories or commits programmatically. It is written in pure C, and the README also points to language bindings usable from Ruby, .NET, Python, Node.js, and Rust. In other words, rather than replacing commands for Git users, it is closer to a component that lets apps call Git features from inside.
Still, the repository's license field is marked NOASSERTION, so the terms of use cannot be judged from the provided material alone. Knowing only that the latest release is v1.9.7 does not reveal the scope of the changes in that version or its current maintenance status either. The range of features that can be integrated into an app can therefore be gauged from the README, but before adoption the license and the changes in that version have to be checked separately.