Add deprecation warning for CodeQL CLIs < 2.9.4

src/codeql.ts

@@ -1,6 +1,7 @@
 import * as fs from "fs";
 import * as path from "path";
 
+import * as core from "@actions/core";
 import * as toolrunner from "@actions/exec/lib/toolrunner";
 import * as yaml from "js-yaml";
 
@@ -270,6 +271,11 @@ let cachedCodeQL: CodeQL | undefined = undefined;
  */
 const CODEQL_MINIMUM_VERSION = "2.8.5";
 
+/**
+ * This version will shortly become the oldest version of CodeQL that the Action will run with.
+ */
+const CODEQL_NEXT_MINIMUM_VERSION = "2.9.4";
+
 /**
  * Versions of CodeQL that version-flag certain functionality in the Action.
  * For convenience, please keep these in descending order. Once a version
@@ -1032,6 +1038,22 @@ export async function getCodeQLForCmd(
     throw new Error(
       `Expected a CodeQL CLI with version at least ${CODEQL_MINIMUM_VERSION} but got version ${await codeql.getVersion()}`
     );
+  } else if (
+    checkVersion &&
+    !(await util.codeQlVersionAbove(codeql, CODEQL_NEXT_MINIMUM_VERSION))
+  ) {
+    core.warning(
+      `CodeQL CLI version ${await codeql.getVersion()} was deprecated on 2023-06-20 alongside ` +
+        "GitHub Enterprise Server 3.5 and will not be supported by the next release of the " +
+        "CodeQL Action. Please update to a newer version of the CodeQL CLI " +
+        `(minimum ${CODEQL_NEXT_MINIMUM_VERSION}). For instance, if you have specified a custom ` +
+        "version of the CLI using the 'tools' input to the 'init' Action, you can remove it to " +
+        "use the default version.\n\n" +
+        "Alternatively, if you want to continue using CodeQL CLI version " +
+        `${await codeql.getVersion()}, you can replace 'github/codeql-action/*@v2' by ` +
+        "'github/codeql-action/*@v2.20.4' in your code scanning workflow to ensure you continue " +
+        "using this version of the CodeQL Action."
+    );
   }
   return codeql;
 }