Add gclient hook that checks local git configuration.

Add gclient hook that checks local git configuration.

It will also verify committers can commit by attempting to push to
a test git repository. It will run only once (or rather once per git
configuration), so it shouldn't significantly increase runhooks
duration.

R=iannucci@chromium.org
BUG=399054
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290653

[Vadim Sh., 2014-08-18 20:57:18]

ptal

[iannucci, 2014-08-19 00:42:29]

lgtm

https://chromiumcodereview.appspot.com/483873003/diff/20001/DEPS
File DEPS (right):

https://chromiumcodereview.appspot.com/483873003/diff/20001/DEPS#newcode821
DEPS:821: # of SVN history forever though.
can drop the last sentence :)

[Vadim Sh., 2014-08-19 00:57:43]

https://chromiumcodereview.appspot.com/483873003/diff/20001/DEPS
File DEPS (right):

https://chromiumcodereview.appspot.com/483873003/diff/20001/DEPS#newcode821
DEPS:821: # of SVN history forever though.
On 2014/08/19 00:42:29, iannucci wrote:
> can drop the last sentence :)

Done.

[Vadim Sh., 2014-08-19 19:54:23]

The CQ bit was checked by vadimsh@chromium.org

[Vadim Sh., 2014-08-19 19:54:52]

The CQ bit was unchecked by vadimsh@chromium.org

[Vadim Sh., 2014-08-19 20:30:32]

The CQ bit was checked by vadimsh@chromium.org

[commit-bot: I haz the power, 2014-08-19 20:31:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vadimsh@chromium.org/483873003/40001

[commit-bot: I haz the power, 2014-08-19 20:32:30]

Committed patchset #3 (40001) as 290653

[kjellander_chromium, 2015-03-16 12:43:45]

On 2014/08/19 20:32:30, I haz the power (commit-bot) wrote:
> Committed patchset #3 (40001) as 290653

I guess it's about time to remove this one, right?