title: How to set the default option as -h for Python click?
body: <h3>How to set the default option as -h for Python click?</h3>
  
  <p>By default, my script, shows nothing when no arguments is given to the <code>duh.py</code>:</p>
  
  <pre><code>import click
  
  
  CONTEXT_SETTINGS = dict(help_option_names=['-h', '--help'])
  
  @click.command(context_settings=CONTEXT_SETTINGS)
  @click.option('--toduhornot', is_flag=True, help='prints "duh..."')
  def duh(toduhornot):
      if toduhornot:
          click.echo('duh...')
  
  if __name__ == '__main__':
      duh()
  </code></pre>
  
  <h3>[out]:</h3>
  
  <pre><code>$ python3 test_click.py -h
  Usage: test_click.py [OPTIONS]
  
  Options:
    --toduhornot  prints "duh..."
    -h, --help    Show this message and exit.
  
  
  
  $ python3 test_click.py --toduhornot
  duh...
  
  
  $ python3 test_click.py 
  </code></pre>
  
  <h3>Question:</h3>
  
  <p>As shown above, the default prints no information <code>python3 test_click.py</code>.</p>
  
  <p>Is there a way such that, the default option is set to <code>-h</code> if no arguments is given, e.g. </p>
  
  <pre><code>$ python3 test_click.py 
  Usage: test_click.py [OPTIONS]
  
  Options:
    --toduhornot  prints "duh..."
    -h, --help    Show this message and exit.
  </code></pre>