Deprecate compatibility with CMake versions older than 3.10

Issue a deprecation warning on calls to `cmake_minimum_required` or
`cmake_policy` that set policies based on versions older than 3.10.
Note that the effective policy version includes `...<max>` treatment.
Update the check from commit 3a4791548d (Deprecate compatibility with
CMake versions older than 3.5, 2023-02-09, v3.27.0-rc1~508^2).

2 files changed, 15 insertions, 0 deletions

diff --git a/Help/command/DEPRECATED_POLICY_VERSIONS.txt b/Help/command/DEPRECATED_POLICY_VERSIONS.txt
index 7c68260..f5104d3 100644
--- a/Help/command/DEPRECATED_POLICY_VERSIONS.txt
+++ b/Help/command/DEPRECATED_POLICY_VERSIONS.txt
@@ -1,3 +1,11 @@
+.. versionchanged:: 3.31
+
+  Compatibility with versions of CMake older than 3.10 is deprecated.
+  Calls to :command:`cmake_minimum_required(VERSION)` or
+  :command:`cmake_policy(VERSION)` that do not specify at least
+  3.10 as their policy version (optionally via ``...<max>``)
+  will produce a deprecation warning in CMake 3.31 and above.
+
 .. versionchanged:: 3.27
 
   Compatibility with versions of CMake older than 3.5 is deprecated.
diff --git a/Help/release/dev/deprecate-pre-3.10.rst b/Help/release/dev/deprecate-pre-3.10.rst
new file mode 100644
index 0000000..7689039
--- /dev/null
+++ b/Help/release/dev/deprecate-pre-3.10.rst
@@ -0,0 +1,7 @@
+deprecate-pre-3.10
+------------------
+
+* Compatibility with versions of CMake older than 3.10 is now deprecated
+  and will be removed from a future version.  Calls to
+  :command:`cmake_minimum_required` or :command:`cmake_policy` that set
+  the policy version to an older value now issue a deprecation diagnostic.