'\'pivot\' is the position of the first changed character, \'delta\' is
how text after it moved.'

def move(self, pivot, delta):

    if (self < pivot):
        return
    if (delta.line == 0):
        if (self.line == pivot.line):
            self.col += delta.col
    elif (delta.line > 0):
        if (self.line == pivot.line):
            self.col += (delta.col - pivot.col)
        self.line += delta.line
    else:
        self.line += delta.line
        if (self.line == pivot.line):
            self.col += ((- delta.col) + pivot.col)
