Suppress spurious warning about overriding cache dir.

git_cache.py

Index: git_cache.py
diff --git a/git_cache.py b/git_cache.py
index 9ef4873874e34557211344623e4b41fadfe7d310..b47b163975d3288a90dafddfdb9128374b23eb5f 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -290,7 +290,10 @@ class OptionParser(optparse.OptionParser):
       global_cache_dir = subprocess.check_output(
           [GIT_EXECUTABLE, 'config', '--global', 'cache.cachepath']).strip()
       if options.cache_dir:
-        logging.warn('Overriding globally-configured cache directory.')
+        if global_cache_dir and (
+            os.path.abspath(options.cache_dir) !=
+            os.path.abspath(global_cache_dir)):
+          logging.warn('Overriding globally-configured cache directory.')
       else:
         options.cache_dir = global_cache_dir
     except subprocess.CalledProcessError: