Collection index link to self.indexes, the order should be:
        1. command argument
        2. environment
        3. default packages directory

def collection_index(self):
        """
        Collection index link to self.indexes, the order should be:
        1. command argument
        2. environment
        3. default packages directory
        """

        indexes = self.options.index
        #add current directory to indexes
        indexes.insert(0, os.getcwd())
        if 'IDO_INDEXES' in os.environ:
            indexes.extend(os.environ['IDO_INDEXES'].split(';'))

        indexes.append(os.path.join(os.path.dirname(__file__), 'packages').replace('\\', '/'))
        return indexes