Make caching more verbose

- Print cache size when saving cache similarly to restoring
- Print restore success similarly to saving
- Print cached file list if debug logging is enabled

See also: https://github.com/actions/cache/issues/471

packages/cache/src/internal/cacheHttpClient.ts

@@ -301,6 +301,10 @@ export async function saveCache(
   // Commit Cache
   core.debug('Commiting cache')
   const cacheSize = utils.getArchiveFileSizeIsBytes(archivePath)
+  core.info(
+    `Cache Size: ~${Math.round(cacheSize / (1024 * 1024))} MB (${cacheSize} B)`
+  )
+
   const commitCacheResponse = await commitCache(httpClient, cacheId, cacheSize)
   if (!isSuccessStatusCode(commitCacheResponse.statusCode)) {
     throw new Error(

packages/cache/src/internal/tar.ts

@@ -113,3 +113,30 @@ export async function createTar(
   ]
   await execTar(args, compressionMethod, archiveFolder)
 }
+
+export async function listTar(
+  archivePath: string,
+  compressionMethod: CompressionMethod
+): Promise<void> {
+  // --d: Decompress.
+  // --long=#: Enables long distance matching with # bits.
+  // Maximum is 30 (1GB) on 32-bit OS and 31 (2GB) on 64-bit.
+  // Using 30 here because we also support 32-bit self-hosted runners.
+  function getCompressionProgram(): string[] {
+    switch (compressionMethod) {
+      case CompressionMethod.Zstd:
+        return ['--use-compress-program', 'zstd -d --long=30']
+      case CompressionMethod.ZstdWithoutLong:
+        return ['--use-compress-program', 'zstd -d']
+      default:
+        return ['-z']
+    }
+  }
+  const args = [
+    ...getCompressionProgram(),
+    '-tf',
+    archivePath.replace(new RegExp(`\\${path.sep}`, 'g'), '/'),
+    '-P'
+  ]
+  await execTar(args, compressionMethod)
+}