Fix patching of commands that contain parameter tokens

Fixes #697

base/changes.txt

@@ -6,6 +6,11 @@ completeness or accuracy and it contains some references to files that
 are not part of the distribution.
 ================================================================================
 
+2021-10-20 Phelype Oleinik  <phelype.oleinik@latex-project.org>
+
+	* ltcmdhooks.dtx (subsubsection{Patching by expansion and redefinition}):
+	Fix patching of commands that contain parameter tokens (gh/697)
+
 2021-10-19  Frank Mittelbach  <Frank.Mittelbach@latex-project.org>
 
 	* ltpara.dtx (subsection{The error messages}):

base/doc/ltnews34.tex

@@ -320,6 +320,19 @@ \subsection{Changed how \cs{RemoveFromHook} treats code that isn't in the hook}
 
 
 
+\subsection{Fix patching of commands that contain parameter tokens}
+
+In the previous release, \LaTeX's hook mechanism was extended to add
+support for hooking into commands using generic \hook{cmd} hooks
+(see~\cite{34:ltnews33}).  The initial version had a bug, in which the
+patching of some commands with a parameter token (normally |#|) in their
+definition would fail with a low-level \TeX{} error.  The bug has been
+fixed, and now patching works for those commands as well.
+%
+\githubissue{697}
+
+
+
 
 \subsection{???}
 
@@ -796,6 +809,10 @@ \subsection{???}
   \emph{\LaTeXe{} news 32}.\\
   \url{https://latex-project.org/news/latex2e-news/ltnews32.pdf}
 
+\bibitem{34:ltnews33} \LaTeX{} Project Team:
+  \emph{\LaTeXe{} news 33}.\\
+  \url{https://latex-project.org/news/latex2e-news/ltnews33.pdf}
+
 \end{thebibliography}