Add functionality for caching with GHES

src/cache-utils.ts

@@ -1,3 +1,5 @@
+import * as cache from '@actions/cache';
+import * as core from '@actions/core';
 import * as exec from '@actions/exec';
 import {supportedPackageManagers, PackageManagerInfo} from './package-managers';
 
@@ -42,3 +44,28 @@ export const getCacheDirectoryPath = async (
 
   return stdout;
 };
+
+export function isGhes(): boolean {
+  const ghUrl = new URL(
+    process.env['GITHUB_SERVER_URL'] || 'https://github.com'
+  );
+  return ghUrl.hostname.toUpperCase() !== 'GITHUB.COM';
+}
+
+export function isCacheFeatureAvailable(): boolean {
+  if (!cache.isFeatureAvailable()) {
+    if (isGhes()) {
+      throw new Error(
+        'Cache action is only supported on GHES version >= 3.5. If you are on version >=3.5 Please check with GHES admin if Actions cache service is enabled or not.'
+      );
+    } else {
+      core.warning(
+        'The runner was not able to contact the cache service. Caching will be skipped'
+      );
+    }
+
+    return false;
+  }
+
+  return true;
+}