libgit2 can be imported via CMake FindPkgConfig module:

    find_package(PkgConfig REQUIRED)
    pkg_check_modules(LIBGIT2 REQUIRED IMPORTED_TARGET libgit2)
    target_link_libraries(main PRIVATE PkgConfig::LIBGIT2)

vcpkg provides proprietary CMake targets:

    find_package(unofficial-libgit2 CONFIG REQUIRED)
    target_link_libraries(main PRIVATE unofficial::libgit2::libgit2)