Distribute git configuration in a versioned file
    
    The kernel-source repository uses a script to set certain git config values
    which are meant to be distributed to all users. This mechanism makes it
    cumbersome to update these configuration values and eventually track their
    history.
    
    For security reasons, git does not have a way to implicitly include
    configuration values in a repository's content. However, we can explicitly
    include extra configuration values from a versioned file using the
    "include.path" configuration directive. Reuse the old mechanism to add this
    directive (which should hopefully not need changes in the future) and
    include the actual configuration values of interest to all users in a
    separate file.
    
    - extra-gitconfig:
    - scripts/install-git-hooks: