Add a RevGitWithRetry method to retry repo sync and git push

Add a RevGitWithRetry method to retry repo sync and git push
Modify repo sync to just sync the repo we are in, 
this is what preflight does and is a proven acceptable approach over
the complete 'repo sync' approach.

BUG=8987
TEST=Ran retry command over dummy directories to be sure it retries
as expected.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=b593c39

[Raja Aluri, 2010-11-16 17:25:17]

LGTM

[scottz, 2010-11-16 17:28:03]

I decided i wanted a back off timeout so I added a 5 second * retry step in
there.

[sosa, 2010-11-16 17:28:43]

LGTM w/ nit

http://codereview.chromium.org/5082002/diff/1/prebuilt.py
File prebuilt.py (right):

http://codereview.chromium.org/5082002/diff/1/prebuilt.py#newcode138
prebuilt.py:138: print 'Error pushing changes trying again (%s/%s)' % (retry,
retries)
Nit: The last error will say trying again even though it's not?

[sosa, 2010-11-16 17:29:49]

http://codereview.chromium.org/5082002/diff/4001/prebuilt.py
File prebuilt.py (right):

http://codereview.chromium.org/5082002/diff/4001/prebuilt.py#newcode140
prebuilt.py:140: time.sleep(5*retry)
nit: You sleep after the last try

You may wanna consider refactoring to check the num of retries in the except
clause rather than a for loop

[scottz, 2010-11-16 17:49:02]

PTAL. I added a check in the except clause to do the right thing.

http://codereview.chromium.org/5082002/diff/4001/prebuilt.py
File prebuilt.py (right):

http://codereview.chromium.org/5082002/diff/4001/prebuilt.py#newcode140
prebuilt.py:140: time.sleep(5*retry)
On 2010/11/16 17:29:50, sosa wrote:
> nit: You sleep after the last try
> 
> You may wanna consider refactoring to check the num of retries in the except
> clause rather than a for loop

Done.

[sosa, 2010-11-16 17:57:33]

LGTM