Integrate by completing the square.
$$\int \limits_0^2 \sqrt{x^2-2x+1}   dx = \int \limits_0^2 \sqrt{(x-1)^2}   dx = \int \limits_0^2 x-1   dx $$
$$ = \left[\frac{1}{2}x^2-x\right]_0^2 $$
$$ =\left(\frac{1}{2}(2)^2-2\right)-\left(\frac{1}{2}(0)^2-0\right) $$
$$ =(2-2)-(0-0) $$
$$ =\boxed{0} $$