All of these sets will be disjoint by construction
(see Invariants, below). Hence:
+\item[ $\set A$, $\set P$, $\ldots$ ]
+Arbitrary sets of commits. Maybe $\set P = \p$ i.e.\ some $\py$ or $\pn$, but
+maybe not.
+
\item[ $ \patchof{ C } $ ]
Either $\p$ s.t. $ C \in \p $, or $\bot$.
A function from commits to patches' sets $\p$.