Function $f$ is defined by $f(x)=(x+6)(x+5)(x+1)$. Function $g$ is defined by $g(x)=f(x-1)$. The graph of $y=g(x)$ in the $xy$-plane has x-intercepts at $(a,0)$, $(b,0)$, and $(c,0)$, where $a$, $b$, and $c$ are distinct constants. What is the value of $a+b+c$?
