"pub cache repair" prints a more detailed summary.

lib/src/source/git.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.git;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as path;
 
@@ skipping 145 matching lines @@
   }
 
   List<Package> getCachedPackages() {
     // TODO(keertip): Implement getCachedPackages().
     throw new UnimplementedError(
         "The git source doesn't support listing its cached packages yet.");
   }
 
   /// Resets all cached packages back to the pristine state of the Git
   /// repository at the revision they are pinned to.
-  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 = [];
 
     var packages = listDir(systemCacheRoot)
         .where((entry) => dirExists(path.join(entry, ".git")))
         .map((packageDir) => new Package.load(null, packageDir,
             systemCache.sources))
         .toList();
 
     // Note that there may be multiple packages with the same name and version
     // (pinned to different commits). The sort order of those is unspecified.
     packages.sort(Package.orderByNameAndVersion);
 
     for (var package in packages) {
+      var id = new PackageId(package.name, this.name, package.version, null);
+
       log.message("Resetting Git repository for "
           "${log.bold(package.name)} ${package.version}...");
 
       try {
         // Remove all untracked files.
         await git.run(["clean", "-d", "--force", "-x"],
             workingDir: package.dir);
 
         // Discard all changes to tracked files.
         await git.run(["reset", "--hard", "HEAD"], workingDir: package.dir);
 
-        successes++;
+        successes.add(id);
       } on git.GitException catch (error, stackTrace) {
         log.error("Failed to reset ${log.bold(package.name)} "
             "${package.version}. Error:\n$error");
         log.fine(stackTrace);
-        failures++;
+        failures.add(id);
 
         tryDeleteEntry(package.dir);
       }
     }
 
     return new Pair(successes, failures);
   }
 
   /// Ensure that the canonical clone of the repository referred to by [id] (the
   /// one in `<system cache>/git/cache`) exists and contains the revision
@@ skipping 121 matching lines @@
     return description['ref'];
   }
 
   /// Returns [description] if it's a description, or [PackageId.description] if
   /// it's a [PackageId].
   _getDescription(description) {
     if (description is PackageId) return description.description;
     return description;
   }
 }