Deprecate TRAP cache cleanup

Author: henrymercer

CHANGELOG.md

@@ -4,6 +4,7 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 
 ## [UNRELEASED]
 
+- The undocumented TRAP cache cleanup feature that could be enabled using the `CODEQL_ACTION_CLEANUP_TRAP_CACHES` environment variable is deprecated and will be removed in May 2026. If you are affected by this, we recommend disabling TRAP caching by passing the `trap-caching: false` input to the `init` Action. [#3795](https://github.com/github/codeql-action/pull/3795)
 - The Git version 2.36.0 requirement for improved incremental analysis now only applies to repositories that contain submodules. [#3789](https://github.com/github/codeql-action/pull/3789)
 - Python analysis on GHES no longer extracts the standard library, relying instead on models of the standard library. This should result in significantly faster extraction and analysis times, while the effect on alerts should be minimal. [#3794](https://github.com/github/codeql-action/pull/3794)
 

lib/analyze-action.js

@@ -185,6 +185,10 @@ export async function cleanupTrapCaches(
       trap_cache_cleanup_skipped_because: "feature disabled",
     };
   }
+  logger.warning(
+    "TRAP cache cleanup is deprecated and will be removed in May 2026. " +
+      "We recommend instead disabling TRAP caching by passing the `trap-caching: false` input to the `init` Action.",
+  );
   if (!(await gitUtils.isAnalyzingDefaultBranch())) {
     return {
       trap_cache_cleanup_skipped_because: "not analyzing default branch",