"pub cache repair" prints a more detailed summary.

lib/src/source/hosted.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library pub.source.hosted;
 
 import 'dart:async';
 import 'dart:io' as io;
 import "dart:convert";
 
@@ skipping 107 matching lines @@
   /// given name from the default host, while a map with keys "name" and "url"
   /// refers to a package with the given name from the host at the given URL.
   dynamic parseDescription(String containingPath, description,
                            {bool fromLockFile: false}) {
     _parseDescription(description);
     return description;
   }
 
   /// Re-downloads all packages that have been previously downloaded into the
   /// system cache from any server.
-  Future<Pair<int, int>> repairCachedPackages() async {
-    if (!dirExists(systemCacheRoot)) return new Pair(0, 0);
+  Future<Pair<List<PackageId>, List<PackageId>>> repairCachedPackages() async {
+    if (!dirExists(systemCacheRoot)) return new Pair([], []);
 
-    var successes = 0;
-    var failures = 0;
+    var successes = [];
+    var failures = [];
 
     for (var serverDir in listDir(systemCacheRoot)) {
       var url = _directoryToUrl(path.basename(serverDir));
       var packages = _getCachedPackagesInDirectory(path.basename(serverDir));
       packages.sort(Package.orderByNameAndVersion);
 
       for (var package in packages) {
+        var id = new PackageId(package.name, this.name, package.version, null);
+
         try {
           await _download(url, package.name, package.version, package.dir);
-          successes++;
+          successes.add(id);
         } catch (error, stackTrace) {
-          failures++;
+          failures.add(id);
           var message = "Failed to repair ${log.bold(package.name)} "
               "${package.version}";
           if (url != defaultUrl) message += " from $url";
           log.error("$message. Error:\n$error");
           log.fine(stackTrace);
 
           tryDeleteEntry(package.dir);
         }
       }
     }
@@ skipping 192 matching lines @@
   var name = description["name"];
   if (name is! String) {
     throw new FormatException("The 'name' key must have a string value.");
   }
 
   var url = description["url"];
   if (url == null) url = HostedSource.defaultUrl;
 
   return new Pair<String, String>(name, url);
 }