Improve branch creation in release scripts.

tools/push-to-trunk/git_recipes.py

Index: tools/push-to-trunk/git_recipes.py
diff --git a/tools/push-to-trunk/git_recipes.py b/tools/push-to-trunk/git_recipes.py
index 7cfbeca0a36e0c730dc8f40745683068b1bd36f2..d57dc848f0bab77d0464586a51b7a6a3d7b37035 100644
--- a/tools/push-to-trunk/git_recipes.py
+++ b/tools/push-to-trunk/git_recipes.py
@@ -105,9 +105,10 @@ class GitRecipesMixin(object):
   def GitBranch(self, **kwargs):
     return self.Git("branch", **kwargs)
 
-  def GitCreateBranch(self, name, branch="", **kwargs):
+  def GitCreateBranch(self, name, remote="", **kwargs):
     assert name
-    self.Git(MakeArgs(["checkout -b", name, branch]), **kwargs)
+    remote_args = ["--upstream", remote] if remote else []
+    self.Git(MakeArgs(["new-branch", name] + remote_args), **kwargs)
 
   def GitDeleteBranch(self, name, **kwargs):
     assert name