Rationalize the git config settings for index-pack performance.

BUG=

Review URL: https://codereview.chromium.org/202753003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@257728 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_cache.py b/git_cache.py
index dfda1d7..9ef4873 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -181,8 +181,8 @@
     d = ['--depth', '%d' % options.depth]
 
   def _config(directory):
-    RunGit(['config', 'core.deltaBaseCacheLimit', '2g'],
-           cwd=directory)
+    RunGit(['config', 'core.deltaBaseCacheLimit',
+            gclient_utils.DefaultDeltaBaseCacheLimit()], cwd=directory)
     RunGit(['config', 'remote.origin.url', url],
            cwd=directory)
     RunGit(['config', '--replace-all', 'remote.origin.fetch',