Refactor Manifest to be XmlManifest

We'll soon be supporting two different manifest formats, but we
can't immediately remove support for the current XML one that is
in wide spread use within Android.

Signed-off-by: Shawn O. Pearce <sop@google.com>

repo

@@ -505,7 +505,7 @@ def _RunSelf(wrapper_path):
   my_git = os.path.join(my_dir, '.git')
 
   if os.path.isfile(my_main) and os.path.isdir(my_git):
-    for name in ['manifest.py',
+    for name in ['git_config.py',
                  'project.py',
                  'subcmds']:
       if not os.path.exists(os.path.join(my_dir, name)):