def lock(backend=None, remote=None):
    '''
    .. versionadded:: 2015.5.0

    Set a fileserver update lock for VCS fileserver backends (:mod:`git
    <salt.fileserver.gitfs>`, :mod:`hg <salt.fileserver.hgfs>`, :mod:`svn
    <salt.fileserver.svnfs>`).

    .. note::

        This will only operate on enabled backends (those configured in
        :conf_master:`fileserver_backend`).

    backend
        Only set the update lock for the specified backend(s).

    remote
        If not None, then any remotes which contain the passed string will have
        their lock cleared. For example, a ``remote`` value of ``*github.com*``
        will remove the lock from all github.com remotes.

    CLI Example:

    .. code-block:: bash

        salt-run fileserver.lock
        salt-run fileserver.lock backend=git,hg
        salt-run fileserver.lock backend=git remote='*github.com*'
        salt-run fileserver.lock remote=bitbucket
    '''
    fileserver = salt.fileserver.Fileserver(__opts__)
    locked, errors = fileserver.lock(back=backend, remote=remote)
    ret = {}
    if locked:
        ret['locked'] = locked
    if errors:
        ret['errors'] = errors
    if not ret:
        return 'No locks were set'
    return ret