Help: declare CMAKE_HOME_DIRECTORY obsolete

Help/manual/cmake-variables.7.rst

@@ -55,7 +55,6 @@ Variables that Provide Information
    /variable/CMAKE_GENERATOR_INSTANCE
    /variable/CMAKE_GENERATOR_PLATFORM
    /variable/CMAKE_GENERATOR_TOOLSET
-   /variable/CMAKE_HOME_DIRECTORY
    /variable/CMAKE_IMPORT_LIBRARY_PREFIX
    /variable/CMAKE_IMPORT_LIBRARY_SUFFIX
    /variable/CMAKE_JOB_POOL_COMPILE
@@ -608,3 +607,11 @@ Variable Expansion Operators
 
    /variable/CACHE
    /variable/ENV
+
+Obsolete Variables
+==================
+
+.. toctree::
+   :maxdepth: 1
+
+   /variable/CMAKE_HOME_DIRECTORY

Help/variable/CMAKE_HOME_DIRECTORY.rst

 CMAKE_HOME_DIRECTORY
 --------------------
 
-Path to top of source tree.
+Path to top of source tree. Same as :variable:`CMAKE_SOURCE_DIR`.
 
-This is the path to the top level of the source tree.
+This is an internal cache entry used to locate the source directory
+when loading a ``CMakeCache.txt`` from a build tree.  It should not
+be used in project code.  The variable :variable:`CMAKE_SOURCE_DIR`
+has the same value and should be preferred.