The minimum value of the twice differentiable function \( f(x) = \displaystyle\int\limits_{0}^{x} e^{\,x-t} f'(t) \, dt - (x^{2} - x + 1) e^{x}, \ x \in \mathbb{R} \) is:
\( -\dfrac{2}{\sqrt{e}} \)
\( -2\sqrt{e} \)
\( -\sqrt{e} \)
\( \dfrac{2}{\sqrt{e}} \)