Add cmake_language(GET_MESSAGE_LOG_LEVEL) sub command

The new sub-command writes a string representation of the
current log level to the output variable given to the
sub-command.

Given that the log-level might be set either via the --log-level
command line option or via the CMAKE_MESSAGE_LOG_LEVEL
cache / regular variables, the priority for each of the log level
sources is as follows, with the first one being the highest:
1) --log-level
2) CMAKE_MESSAGE_LOG_LEVEL regular variable
3) CMAKE_MESSAGE_LOG_LEVEL cache variable
4) default log level (STATUS)

Fixes: #23572

1 files changed, 26 insertions, 0 deletions

diff --git a/Help/command/cmake_language.rst b/Help/command/cmake_language.rst
index cb8d60b..377e42d 100644
--- a/Help/command/cmake_language.rst
+++ b/Help/command/cmake_language.rst
@@ -14,6 +14,7 @@ Synopsis
   cmake_language(`EVAL`_ CODE <code>...)
   cmake_language(`DEFER`_ <options>... CALL <command> [<arg>...])
   cmake_language(`SET_DEPENDENCY_PROVIDER`_ <command> SUPPORTED_METHODS <methods>...)
+  cmake_language(`GET_MESSAGE_LOG_LEVEL`_ <out-var>)
 
 Introduction
 ^^^^^^^^^^^^
@@ -491,3 +492,28 @@ calling the provider command recursively for the same dependency.
     SET_DEPENDENCY_PROVIDER mycomp_provide_dependency
     SUPPORTED_METHODS FIND_PACKAGE
   )
+
+Getting current message log level
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. versionadded:: 3.25
+
+.. _GET_MESSAGE_LOG_LEVEL:
+.. _query_message_log_level:
+
+.. code-block:: cmake
+
+  cmake_language(GET_MESSAGE_LOG_LEVEL <output_variable>)
+
+Writes the current :command:`message` logging level
+into the given ``<output_variable>``.
+
+See :command:`message` for the possible logging levels.
+
+The current message logging level can be set either using the ``--log-level``
+command line option of the :manual:`cmake(1)` program or using
+the :variable:`CMAKE_MESSAGE_LOG_LEVEL` variable.
+
+If both the command line option and the variable are set, the command line
+option takes precedence. If neither are set, the default logging level
+is returned.