Use a bare git repository for the repo cache.

utils/tests/pub/test_pub.dart

Index: utils/tests/pub/test_pub.dart
diff --git a/utils/tests/pub/test_pub.dart b/utils/tests/pub/test_pub.dart
index 6fbee3042af1a98159cd708834f84d8c76837ba9..b70f25b123151374dfc95d3c15142e3878e640b5 100644
--- a/utils/tests/pub/test_pub.dart
+++ b/utils/tests/pub/test_pub.dart
@@ -292,9 +292,9 @@ DirectoryDescriptor packageCacheDir(String name, String version) {
 
 /**
  * Describes a directory for a Git package. This directory is of the form found
- * in the global package cache.
+ * in the revision cache of the global package cache.
  */
-DirectoryDescriptor gitPackageCacheDir(String name, [int modifier]) {
+DirectoryDescriptor gitPackageRevisionCacheDir(String name, [int modifier]) {
   var value = name;
   if (modifier != null) value = "$name $modifier";
   return dir(new RegExp("$name${@'-[a-f0-9]+'}"), [
@@ -303,6 +303,20 @@ DirectoryDescriptor gitPackageCacheDir(String name, [int modifier]) {
 }
 
 /**
+ * Describes a directory for a Git package. This directory is of the form found
+ * in the repo cache of the global package cache.
+ */
+DirectoryDescriptor gitPackageRepoCacheDir(String name) {
+  return dir(new RegExp("$name${@'-[a-f0-9]+'}"), [
+    dir('branches'),
+    dir('hooks'),
+    dir('info'),
+    dir('objects'),
+    dir('refs')
+  ]);
+}
+
+/**
  * Describes the `packages/` directory containing all the given [packages],
  * which should be name/version pairs. The packages will be validated against
  * the format produced by the mock package server.
@@ -815,7 +829,9 @@ class DirectoryDescriptor extends Descriptor {
    */
   final List<Descriptor> contents;
 
-  DirectoryDescriptor(Pattern name, this.contents) : super(name);
+  DirectoryDescriptor(Pattern name, List<Descriptor> contents)
+    : this.contents = contents == null ? <Descriptor>[] : contents,
+      super(name);
 
   /**
    * Creates the file within [dir]. Returns a [Future] that is completed after
@@ -958,6 +974,14 @@ class GitRepoDescriptor extends DirectoryDescriptor {
     return completer.future;
   }
 
+  /// Schedule a Git command to run in this repository.
+  void scheduleGit(List<String> args) {
+    _schedule((parentDir) {
+      var gitDir = new Directory(join(parentDir, name));
+      return _runGit(args, gitDir);
+    });
+  }
+
   Future<String> _runGit(List<String> args, Directory workingDir) {
     return runProcess('git', args, workingDir: workingDir.path).
       transform((result) {