-sponge
-$ C \hasparents X $
-$ C > X $
-$ X \areparents C $
-$ X < C $
-$ D \isin C $
-$ A \sqsubseteq B $
-$ A \not \sqsubseteq B $
-$ A \nsqsubseteq B $
-$ A \le B $
-$ A \Sqsubset B $
-$ A \Sqsupset B $
-$ A \haspatch B $
-$ A \nothaspatch B $
-$ A \patchisin B $
-$ A \notpatchisin B $
-$ A \nothaspatch \pa{C} $
-$ A \nothaspatch \py $
-$ A \nothaspatch \p_C^+ $
-$ A \nothaspatch \pan{C} $
+\section{Notation}
+
+$ C \hasparents \set X $ The parents of commit $C$ are exactly the set
+$\set X$.
+
+$ 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 $.
+
+$ 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.
+
+\section{Invariants}
+
+No rewind/replay: $ C \has D \implies C \ge D $
+