refactor(config/global): Enable strict null checks (#12867)

* refactor(config/global): Enable strict null checks

* Fix inefficient copying

Co-authored-by: Rhys Arkins <rhys@arkins.net>

lib/config/global.ts

@@ -2,7 +2,7 @@ import type { RenovateConfig, RepoGlobalConfig } from './types';
 
 export class GlobalConfig {
   // TODO: once global config work is complete, add a test to make sure this list includes all options with globalOnly=true (#9603)
-  private static readonly OPTIONS = [
+  private static readonly OPTIONS: (keyof RepoGlobalConfig)[] = [
     'allowCustomCrateRegistries',
     'allowedPostUpgradeCommands',
     'allowPlugins',
@@ -40,7 +40,7 @@ export class GlobalConfig {
 
     const result = { ...config };
     for (const option of GlobalConfig.OPTIONS) {
-      GlobalConfig.config[option] = config[option];
+      GlobalConfig.config[option] = config[option] as never;
       delete result[option];
     }
 

tsconfig.strict.json

@@ -7,6 +7,7 @@
   },
   "files": [
     "./lib/config/app-strings.ts",
+    "./lib/config/global.ts",
     "./lib/config/migrations/types.ts",
     "./lib/config/presets/common.ts",
     "./lib/constants/error-messages.ts",