Add gclient style cache_dir support for deps2git.

Add gclient style cache_dir support for deps2git.

Also - During clone, always pipe stdout to sys.stdout. This will not work as well when we want to multithread
deps2git, but will be okay for now to get buildbot to not kill the process when checking out blink.

BUG=339168
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=249599

[Ryan Tseng, 2014-02-07 00:45:26]

szager for review - ptal

This does 2 things:
1. Add a --cached_dir flag so that gclient can reuse the git repos checked out
by deps2git.py (which does a cached checkout using --bare rather than --mirror)
2. Pipes all git clone output directly to sys.stdout.

[Ryan Tseng, 2014-02-07 01:31:39]

Actually this makes more sense:
szager for review on GetStatusOutput()
iannucci for review on --cached_dir.

[agable, 2014-02-07 03:28:32]

LGTM % nit.

https://codereview.chromium.org/150653004/diff/30001/deps2git.py
File deps2git.py (right):

https://codereview.chromium.org/150653004/diff/30001/deps2git.py#newcode33
deps2git.py:33: url = url[idx+3:]
separator = '://'
url = url[idx+len(separator):]
etc.

[Ryan Tseng, 2014-02-07 03:35:52]

Fixed

Szager: In the interest of landing bot_update.py today, I'm going to commit this
patch now.  If there are any other comments I will fix it in another CL.

[Ryan Tseng, 2014-02-07 03:36:11]

The CQ bit was checked by hinoka@google.com

[commit-bot: I haz the power, 2014-02-07 03:36:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hinoka@google.com/150653004/80001

[commit-bot: I haz the power, 2014-02-07 03:36:27]

Change committed as 249599

[szager, 2014-02-07 14:09:29]

lgtm

https://codereview.chromium.org/150653004/diff/80001/deps2git.py
File deps2git.py (right):

https://codereview.chromium.org/150653004/diff/80001/deps2git.py#newcode31
deps2git.py:31: separator = '://'
In general, use the urlparse package for url slicing and dicing.