Fix SCM.ReadRootFile when self.gclient_root is not yet defined

trychange.py

Index: trychange.py
===================================================================
--- trychange.py	(revision 47310)
+++ trychange.py	(working copy)
@@ -158,8 +158,11 @@
         logging.info('Found %s at %s' % (filename, self.checkout_root))
         return gclient_util.FileRead(filepath)
       return None
-    root = os.path.abspath(self.gclient_root)
     cur = os.path.abspath(self.checkout_root)
+    if self.gclient_root:
+      root = os.path.abspath(self.gclient_root)
+    else:
+      root = gclient_utils.FindGclientRoot(cur)

[M-A Ruel, 2010/05/15 00:53:14]

As I wrote earlier, I still prefer to use root = cur since if you specify a
root, you usually don't want it to mess with interwinded checkouts.

     assert cur.startswith(root), (root, cur)
     while cur.startswith(root):
       filepath = os.path.join(cur, filename)