Skip updating remotes if we already have the upstream revision.

Skip updating remotes if we already have the upstream revision.

This should make a `gclient sync` faster, especially on Windows, where git hangs regularly.

BUG=none
TEST=gclient sync -v doesn't print "Fetching origin" all the time


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=143898
Reverted: http://src.chromium.org/viewvc/chrome?view=rev&revision=143911

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=144451

[Bernhard Bauer, 2012-06-25 12:11:46]

Please review.

[M-A Ruel, 2012-06-25 12:16:34]

Thanks! I wanted to look at that for a while but never took the time. That's
appreciated.

lgtm

[commit-bot: I haz the power, 2012-06-25 12:26:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/bauerb@chromium.org/10668020/1

[commit-bot: I haz the power, 2012-06-25 12:29:36]

Change committed as 143898

[commit-bot: I haz the power, 2012-06-27 13:46:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/bauerb@chromium.org/10668020/6001

[commit-bot: I haz the power, 2012-06-27 13:49:28]

Change committed as 144451