Help: Clarify ...<max> behavior for policy-related commands

Affects cmake_minimum_required() and cmake_policy(VERSION)

Help/command/cmake_minimum_required.rst

@@ -13,6 +13,10 @@ If the running version of CMake is lower than the ``<min>`` required
 version it will stop processing the project and report an error.
 The optional ``<max>`` version, if specified, must be at least the
 ``<min>`` version and affects policy settings as described below.
+If the running version of CMake is older than 3.12, the extra ``...``
+dots will be seen as version component separators, resulting in the
+``...<max>`` part being ignored and preserving the pre-3.12 behavior
+of basing policies on ``<min>``.
 
 The ``FATAL_ERROR`` option is accepted but ignored by CMake 2.6 and
 higher.  It should be specified so CMake versions 2.4 and lower fail

Help/command/cmake_policy.rst

@@ -30,7 +30,10 @@ encourage projects to set policies based on CMake versions::
 ``major.minor[.patch[.tweak]]``, and the ``...`` is literal.  The ``<min>``
 version must be at least ``2.4`` and at most the running version of CMake.
 The ``<max>`` version, if specified, must be at least the ``<min>`` version
-but may exceed the running version of CMake.
+but may exceed the running version of CMake.  If the running version of
+CMake is older than 3.12, the extra ``...`` dots will be seen as version
+component separators, resulting in the ``...<max>`` part being ignored and
+preserving the pre-3.12 behavior of basing policies on ``<min>``.
 
 This specifies that the current CMake code is written for the given
 range of CMake versions.  All policies known to the running version of CMake

Help/release/3.12.rst

@@ -34,7 +34,8 @@ Commands
 * The :command:`cmake_minimum_required` and :command:`cmake_policy(VERSION)`
   commands now accept a version range using the form ``<min>[...<max>]``.
   The ``<min>`` version is required but policies are set based on the
-  ``<max>`` version.  This allows projects to specify a range of versions
+  older of the running CMake version and the version specified by
+  ``<max>``.  This allows projects to specify a range of versions
   for which they have been updated and avoid explicit policy settings.
 
 * The :command:`file(GLOB)` and :command:`file(GLOB_RECURSE)` commands