\item[ $h : \pc^{+/-} \mapsto \set H^{\pc^{+/-}}$ ]
Function for getting the existing heads $\set H$ of the branch $\pc^{+/-}$.
-\item[ $w : \pc^{+/-} \mapsto \set W_0^{\pc^{+/-}}$ ]
+\item[ $w : \pc^{+/-} \mapsto W_0^{\pc^{+/-}}$ ]
Function for getting the existing local head of the branch
$\pc^{+/-}$. I.e., the current value of the branch ref for $\pc^{+/-}$.