Forget about tracking each file in the list file_names

    Tracking does not create or delete the actual file, it only tells the
    version control system whether to maintain versions (to keep track) of
    the file.

def untrack(context, file_names):
    """Forget about tracking each file in the list file_names

    Tracking does not create or delete the actual file, it only tells the
    version control system whether to maintain versions (to keep track) of
    the file.
    """
    context.obj.find_repo_type()
    for fn in file_names:
        if context.obj.vc_name == 'git':
            context.obj.call(['git', 'rm', '--cached', fn])
        elif context.obj.vc_name == 'hg':
            context.obj.call(['hg', 'forget', fn])