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

git_rebase_update.py

@@ -64,10 +64,8 @@ def fetch_remotes(branch_tree):
   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):

testing_support/git_test_utils.py

@@ -14,8 +14,6 @@ import sys
 import tempfile
 import unittest
 
-from cStringIO import StringIO
-
 
 def git_hash_data(data, typ='blob'):
   """Calculate the git-style SHA1 for some data.
@@ -395,13 +393,17 @@ class GitRepo(object):
     stdout = sys.stdout
     stderr = sys.stderr
     try:
-      sys.stdout = StringIO()
-      sys.stderr = StringIO()
-      try:
-        self.run(fn, *args, **kwargs)
-      except SystemExit:
-        pass
-      return sys.stdout.getvalue(), sys.stderr.getvalue()
+      # "multiple statements on a line" pylint: disable=C0321
+      with tempfile.TemporaryFile() as out, tempfile.TemporaryFile() as err:
+        sys.stdout = out
+        sys.stderr = err
+        try:
+          self.run(fn, *args, **kwargs)
+        except SystemExit:
+          pass
+        out.seek(0)
+        err.seek(0)
+        return out.read(), err.read()
     finally:
       sys.stdout = stdout
       sys.stderr = stderr