Utilities/Sphinx: Add role and directive for 'genex' in CMake domain

This enables cross-reference syntax for CMake generator expressions:

    :genex:`SOME_GENEX`
    :genex:`$<SOME_GENEX>`
    :genex:`$<SOME_GENEX:...>`

and definition of CMake generator expressions via a directive:

    .. genex:: SOME_GENEX
    .. genex:: $<SOME_GENEX>
    .. genex:: $<SOME_GENEX:...>

It also adds generator expressions defined by the directive and by
`Help/genex/SOME_GENEX.rst` documents to the index.

1 files changed, 13 insertions, 2 deletions

diff --git a/Help/dev/documentation.rst b/Help/dev/documentation.rst
index e34c754..29fc880 100644
--- a/Help/dev/documentation.rst
+++ b/Help/dev/documentation.rst
@@ -136,6 +136,10 @@ documentation:
  A CMake native build system generator.
  See the `cmake(1)`_ command-line tool's ``-G`` option.
 
+``genex``
+ A CMake generator expression.
+ See the `cmake-generator-expressions(7)`_ manual.
+
 ``manual``
  A CMake manual page, like the `cmake(1)`_ manual.
 
@@ -169,10 +173,12 @@ which is expected to be of the form::
  -------------
 
 and to appear at or near the top of the ``.rst`` file before any other
-lines starting in a letter, digit, or ``<``.  If no such title appears
+lines starting in a letter, digit, ``<``, or ``$``.  If no such title appears
 literally in the ``.rst`` file, the object name is the ``<file-name>``.
 If a title does appear, it is expected that ``<file-name>`` is equal
-to ``<object-name>`` with any ``<`` and ``>`` characters removed.
+to ``<object-name>`` with any ``<`` and ``>`` characters removed,
+or in the case of a ``$<genex-name>`` or ``$<genex-name:...>``, the
+``genex-name``.
 
 Second, the CMake Domain provides directives to define objects inside
 other documents:
@@ -187,6 +193,10 @@ other documents:
 
   This indented block documents <envvar-name>.
 
+ .. genex:: <genex-name>
+
+  This indented block documents <genex-name>.
+
  .. variable:: <variable-name>
 
   This indented block documents <variable-name>.
@@ -197,6 +207,7 @@ the first approach above.
 .. _`Sphinx Domain`: http://sphinx-doc.org/domains.html
 .. _`cmake(1)`: https://cmake.org/cmake/help/latest/manual/cmake.1.html
 .. _`cmake-env-variables(7)`: https://cmake.org/cmake/help/latest/manual/cmake-env-variables.7.html
+.. _`cmake-generator-expressions(7)`: https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html
 .. _`cmake-modules(7)`: https://cmake.org/cmake/help/latest/manual/cmake-modules.7.html
 .. _`cmake-policies(7)`: https://cmake.org/cmake/help/latest/manual/cmake-policies.7.html
 .. _`cmake-properties(7)`: https://cmake.org/cmake/help/latest/manual/cmake-properties.7.html