+
+\section{Notation}
+
+\begin{basedescript}{
+\desclabelwidth{5em}
+\desclabelstyle{\nextlinelabel}
+}
+\item[ $ C \hasparents \set X $ ]
+The parents of commit $C$ are exactly the set
+$\set X$.
+
+\item[ $ C \ge D $ ]
+$C$ is a descendant of $D$ in the git commit
+graph. This is a partial order, namely the transitive closure of
+$ D \in \set X $ where $ C \hasparents \set X $.
+
+\item[ $ C \has D $ ]
+Informally, the tree at commit $C$ contains the change
+made in commit $D$. Does not take account of deliberate reversions by
+the user or in non-Topbloke-controlled branches; these are considered
+normal, forward, commits. For merges and Topbloke-generated
+anticommits, the ``change made'' is only to be thought of as any
+conflict resolution. This is not a partial order because it is not
+transitive.
+
+\item[ $ \p, \py, \pn $ ]
+A patch $\p$ consists of two sets of commits $\pn$ and $\py$, which
+are respectively the base and tip git branches. $\p$ may be used
+where the context requires a set, in which case the statement
+is to be taken as applying to both $\py$ and $\pn$.
+All these sets are distinct.
+
+\item[ $ \pancs{C}{\set P} $ ]
+$ \{ A \; | \; A \le C \land A \in \set P \} $
+i.e. all the ancestors of $C$
+which are in $\set P$.
+
+\item[ $ \pends{C}{\set P} $ ]
+$ \{ E \; | \; E \in \pancs{C}{\set P}
+ \land \mathop{\not\exists}_{A \in \pancs{C}{\set P}}
+ A \neq E \land E \le A \} $
+i.e. all $\le$-maximal commits in $\pancs{C}{\set P}$.
+
+\end{basedescript}
+
+\section{Invariants}
+
+\[ C \has D \implies C \ge D \tag*{\mbox{No replay:}} \]
+
+Unique base: \[ \mathop{\forall}_{C \in \py} \pends{C}{\pn} = \{ B \} \]
+
+\section{Test more symbols}
+
+$ C \haspatch \p $
+
+$ C \nothaspatch \p $
+
+$ \p \patchisin C $
+
+$ \p \notpatchisin C $
+
+$ \{ B \} \areparents C $
+