so $R^- \le L$. So $R^+ \le C$ and $R^- \le C$.
$\qed$
-(Note that the merge base $R^+ \not\le R^-$, i.e. the merge base is
-later than one of the branches to be merged.)
+(Note that $R^+ \not\le R^-$, i.e. the merge base
+is a descendant, not an ancestor, of the 2nd parent.)
\subsection{No Replay}