Docs

base/ltclass.dtx

@@ -1176,6 +1176,10 @@
     \@ifundefined{opt@\reserved@a}\@empty
       {\csname opt@\reserved@a\endcsname,}%
     \zap@space#2 \@empty}
+%    \end{macrocode}
+% \changes{v1.3u}{2020/11/14}
+%         {Copy option list to the requested package.}
+%    \begin{macrocode}
   \expandafter\let
     \csname opt@#3.#1\expandafter\endcsname
     \csname opt@\reserved@a\endcsname}
@@ -1838,6 +1842,10 @@
 %    \cs{@currname} which doesn't have a path attached to it;  only few
 %    actions prepend \cs{@currpath} to \cs{@currname} (namely loading,
 %    as we have to respect the given path).
+%
+%    A file substituiton isn't followed just yet because at this point
+%    we are parsing user input, so the file is still what the user
+%    asked for, and not the file actually loaded.
 %    \begin{macrocode}
   \@expl@@@filehook@set@curr@file@@nNN{#1.#4}\reserved@a\reserved@b
   \edef\reserved@c{\def\noexpand\reserved@c####1%
@@ -2023,6 +2031,10 @@
 %    \begin{macrocode}
   \def\reserved@a{%
     \@pass@ptions\@currext{#1}{\@currname}%
+%    \end{macrocode}
+% \changes{v1.3u}{2020/11/14}
+%         {Copy option list to the requested package.}
+%    \begin{macrocode}
     \expandafter\let
       \csname opt@\@currpkg@reqd\expandafter\endcsname
       \csname opt@\@currname.\@currext\endcsname

base/ltfilehook.dtx

@@ -1080,11 +1080,15 @@
 %
 % \begin{macro}{flag @@_file_replaced}
 % \begin{macro}{\@@_if_file_replaced:TF}
+% \begin{macro}{\@@_clear_replacement_flag:}
 %   Since the file replacement is done expandably in a \cs{csname}, use
 %   a flag to remember if a substitution happened.  We use this in
 %   \cs{set@curr@file} to short-circuit some of it in case no
 %   substitution happened (by far the most common case, so it's worth
-%   optimising).
+%   optimising).  The flag raised during the file substitution algorithm
+%   must be explicitly cleared after the \cs{@@_if_file_replaced:TF}
+%   conditional is no longer needed, otherwise further uses of
+%   \cs{@@_if_file_replaced:TF} will wrongly return true.
 %    \begin{macrocode}
 \flag_new:n { @@_file_replaced }
 \cs_new:Npn \@@_if_file_replaced:TF #1 #2
@@ -1094,6 +1098,7 @@
 %    \end{macrocode}
 % \end{macro}
 % \end{macro}
+% \end{macro}
 %
 % \begin{macro}{\@@_file_subst_begin:nnn}
 %   First off, start by checking if the current file ($\meta{name} +