Make git rebase-update more responsive.

Passes through git-fetch's output instead of buffering it.

R=djacques@chromium.org
TBR=agable@chromium.org
BUG=366375

Review URL: https://codereview.chromium.org/264423002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@269080 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_rebase_update.py b/git_rebase_update.py
index 4e96c69..f87f43b 100755
--- a/git_rebase_update.py
+++ b/git_rebase_update.py
@@ -64,10 +64,8 @@
   if not fetch_args:  # pragma: no cover
     print 'Nothing to fetch.'
   else:
-    out, err = git.run_with_stderr('fetch', *fetch_args)
-    for data, stream in zip((out, err), (sys.stdout, sys.stderr)):
-      if data:
-        print >> stream, data
+    git.run_with_stderr('fetch', *fetch_args, stdout=sys.stdout,
+                        stderr=sys.stderr)
 
 
 def remove_empty_branches(branch_tree):