Log Message:
libgit2: Update to 0.28.3

This is a security release fixing the following issues:

    A carefully constructed commit object with a very large number
    of parents may lead to potential out-of-bounds writes or
    potential denial of service.

    The ProgramData configuration file is always read for compatibility
    with Git for Windows and Portable Git installations. The ProgramData
    location is not necessarily writable only by administrators, so we
    now ensure that the configuration file is owned by the administrator
    or the current user.