You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spm_update.m
    path of file: ./repos/ExploreASL/External/SPMmodified
    
    the code of the file until where you have to start completion: function varargout = spm_update(update)
% Check (and install) SPM updates from the FIL server
% FORMAT spm_update
% This function will contact the FIL server, compare the version number of
% the updates with the one of the SPM installation currently in the MATLAB
% path and display the outcome.
%
% FORMAT spm_update(update)
% Invoking this function with any input parameter will do the same as
% above but will also attempt to download and install the updates.
% Note that it will close any open window and clear the workspace.
%
% FORMAT [sts, msg] = spm_update(update)
% sts  - status code:
%        NaN - SPM server not accessible
%        Inf - no updates available
%        0   - SPM installation up to date
%        n   - new revision <n> is available for download
% msg  - string describing outcome, that would otherwise be displayed.
%__________________________________________________________________________
% Copyright (C) 2010-2017 Wellcome Trust Centre for Neuroimaging

% Guillaume Flandin

    
function varargout = spm_update(update)
% Check (and install) SPM updates from the FIL server
% FORMAT spm_update
% This function will contact the FIL server, compare the version number of
% the updates with the one of the SPM installation currently in the MATLAB
% path and display the outcome.
%
% FORMAT spm_update(update)
% Invoking this function with any input parameter will do the same as
% above but will also attempt to download and install the updates.
% Note that it will close any open window and clear the workspace.
%
% FORMAT [sts, msg] = spm_update(update)
% sts  - status code:
%        NaN - SPM server not accessible
%        Inf - no updates available
%        0   - SPM installation up to date
%        n   - new revision <n> is available for download
% msg  - string describing outcome, that would otherwise be displayed.
%__________________________________________________________________________
% Copyright (C) 2010-2017 Wellcome Trust Centre for Neuroimaging

% Guillaume Flandin
% $Id: spm_update.m 7218 2017-11-16 10:03:14Z guillaume $


vspm = spm('Ver');
url  = ['http://www.fil.ion.ucl.ac.uk/spm/download/' lower(vspm) '_updates/'];

if ~nargin
    update = false;
else
    update = true;
end