Add a fallback to origin/trunk too when the branch is not tracked.

trychange.py

Index: trychange.py
diff --git a/trychange.py b/trychange.py
index 644a55a915f406a1515f9260b7b35bfdfddaa4d6..cf60b3cffe9b2fabcb77b7133d3c490cc312cbab 100755
--- a/trychange.py
+++ b/trychange.py
@@ -216,9 +216,10 @@ class GIT(SCM):
     if not self.diff_against:
       self.diff_against = scm.GIT.GetUpstreamBranch(self.checkout_root)
       if not self.diff_against:
-        print "Unable to determine default branch to diff against."
-        print "Verify this branch is set up to track another"
-        print "(via the --track argument to \"git checkout -b ...\""
+        raise NoTryServerAccess(
+            "Unable to determine default branch to diff against. "
+            "Verify this branch is set up to track another"
+            "(via the --track argument to \"git checkout -b ...\"")
     logging.info("GIT(%s)" % self.checkout_root)
 
   def ReadRootFile(self, filename):