import re


def sentences_github(text):
    """ Returns a list of sentences in some text that contain a mention of github
    
    The sentences might not necessarily contain a properly formatted repository URL.
    For example, this function can be used to extract sentences that *may* contain a
    repository URL, because the regex to subsequently identify properly formatted 
    repository URLs is less efficient.
    
    Args:
        text: A string containing some text
        
    Returns:
        List of sentences that contain a mention of github
    
    """
    if text is None:
        return []
    formatted = re.sub('[\s\n\r]+', ' ', re.sub('-\n', '-', re.sub('/\n', '/', text)))
    sentences = re.split('[.?!]\s+', formatted)
    return filter(re.compile('[gG]it[hH]ub').search, sentences)