Fix merge-to-branch options.

tools/push-to-trunk/merge_to_branch.py

Index: tools/push-to-trunk/merge_to_branch.py
diff --git a/tools/push-to-trunk/merge_to_branch.py b/tools/push-to-trunk/merge_to_branch.py
index 43f47b40745fceba86c063b4343a051c71422568..7d5f53f3d45ac02448c99ddb11789f8919dfbd70 100755
--- a/tools/push-to-trunk/merge_to_branch.py
+++ b/tools/push-to-trunk/merge_to_branch.py
@@ -52,11 +52,11 @@ CONFIG = {
 
 class MergeToBranchOptions(CommonOptions):
   def __init__(self, options, args):
-    super(MergeToBranchOptions, self).__init__(options, options.m)
+    super(MergeToBranchOptions, self).__init__(options, True)
     self.requires_editor = True
     self.wait_for_lgtm = True
     self.delete_sentinel = options.f
-    self.message = options.m
+    self.message = getattr(options, "message", "")
     self.revert = "--reverse" if getattr(options, "r", None) else ""
     self.revert_bleeding_edge = getattr(options, "revert_bleeding_edge", False)
     self.patch = getattr(options, "p", "")