Add a consensus rule in \crossref{merkletree} that a block MUST NOT add note commitments that

exceed the capacity of each of the Sprout, Sapling, and Orchard note commitment trees.

Also add a cross-reference for constants used in \crossref{merkletree}.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -3559,6 +3559,10 @@ the same \transaction.
 \introsection
 \lsubsection{Note Commitment Trees}{merkletree}
 
+Let $\MerkleHashLength{Sprout}$, $\MerkleDepth{Sprout}$\sapling{, $\MerkleHashLength{Sapling}$,\notnufive{ and }
+$\MerkleDepth{Sapling}$}\nufive{, $\MerkleHashLength{Orchard}$, and $\MerkleDepth{Orchard}$} be as
+defined in \crossref{constants}.
+
 \vspace{-2ex}
 \begin{center}
 \includegraphics[scale=.4]{incremental_merkle}
@@ -3587,6 +3591,19 @@ The \merkleIndex of a \notesCommitment at the leafmost layer
 ($\MerkleDepth{Sprout}$\sapling{ or $\MerkleDepth{Sapling}$}\nufive{ or $\MerkleDepth{Orchard}$})
 is called its \defining{\notePosition}.
 
+\begin{consensusrules}
+  \item A \block \MUSTNOT add \Sprout \noteCommitments that would result in the
+        \Sprout \noteCommitmentTree exceeding its capacity of $2^{\MerkleDepth{Sprout}}$
+        \merkleLeafNodes.
+  \saplingonwarditem{A \block \MUSTNOT add \Sapling \noteCommitments that would result in the
+        \Sapling \noteCommitmentTree exceeding its capacity of $2^{\MerkleDepth{Sapling}}$
+        \merkleLeafNodes.}
+  \nufiveonwarditem{A \block \MUSTNOT add \Orchard \noteCommitments that would result in the
+        \Orchard \noteCommitmentTree exceeding its capacity of $2^{\MerkleDepth{Orchard}}$
+        \merkleLeafNodes.}
+\end{consensusrules}
+
+
 \lsubsection{Nullifier Sets}{nullifierset}
 
 Each \fullValidator maintains a \defining{\nullifierSet} logically associated with
@@ -14473,6 +14490,14 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 \lsection{Change History}{changehistory}
 
 
+\historyentry{2021.2.13}{2021-07-29}
+\begin{itemize}
+    \item Add consensus rules in \crossref{merkletree} that a \block \MUSTNOT add
+          \noteCommitments that exceed the capacity of any of the \Sprout\sapling{ and
+          \Sapling}\nufive{ and \Orchard} \noteCommitmentTrees.
+\end{itemize}
+
+
 \historyentry{2021.2.12}{2021-07-29}
 \begin{itemize}
 \nufive{