Tutorial: Restore source archive when published on cmake.org

Restore commit 4cb616fed6 (Tutorial: Provide a source archive when
published on cmake.org, 2022-04-27, v3.23.2~22^2).  Its effects were
accidentally reverted by commit 9784834b4c (Help: Use `*.rst` extension
for included files, 2025-04-07, v4.1.0-rc1~354^2).

Reported-by: Vito Gamberini <[email protected]>

Help/guide/tutorial/include/source.rst

@@ -0,0 +1,3 @@
+.. |tutorial_source| replace::
+  The tutorial documentation and source code examples can be found in
+  the ``Help/guide/tutorial`` directory of the CMake source code tree.

Help/guide/tutorial/index.rst

@@ -11,8 +11,9 @@ work together in an example project can be very helpful.
 Steps
 =====
 
-The tutorial documentation and source code examples can be found in
-the ``Help/guide/tutorial`` directory of the CMake source code tree.
+.. include:: include/source.rst
+
+|tutorial_source|
 Each step has its own subdirectory containing code that may be used as a
 starting point. The tutorial examples are progressive so that each step
 provides the complete solution for the previous step.

Utilities/Sphinx/tutorial_archive.cmake

@@ -14,7 +14,7 @@ file(COPY "${help_dir}/guide/tutorial/"
   DESTINATION "${CMAKE_CURRENT_BINARY_DIR}/${archive_name}"
   NO_SOURCE_PERMISSIONS
   PATTERN *.rst EXCLUDE
-  PATTERN source.txt EXCLUDE
+  REGEX "/guide/tutorial/include$" EXCLUDE
   )
 file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/${archive_name}/README.txt" [[
 This directory contains source code examples for the CMake Tutorial.
@@ -32,11 +32,11 @@ file(ARCHIVE_CREATE
   )
 
 # Write a reStructuredText snippet included from the tutorial index.
-file(WRITE "${help_dir}/guide/tutorial/source.txt" "
+file(WRITE "${help_dir}/guide/tutorial/include/source.rst" [[
 .. |tutorial_source| replace::
   The tutorial source code examples are available in
-  :download:`this archive </_generated/${archive_name}.zip>`.
-")
+  :download:`this archive </_generated/]] "${archive_name}" [[.zip>`.
+]])
 
 # Remove temporary directory.
 file(REMOVE_RECURSE "${CMAKE_CURRENT_BINARY_DIR}/${archive_name}")