Add `gclient root` command which outputs the current solution's root.

Add `gclient root` command which outputs the current solution's root.

NOPRESUBMIT=true

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295075

[ghost stip (do not use), 2015-04-29 22:49:06]

stip@chromium.org changed reviewers:
+ maruel@chromium.org

[ghost stip (do not use), 2015-04-29 22:49:10]

ptal

[M-A Ruel, 2015-04-29 22:57:08]

lgtm

[M-A Ruel, 2015-04-29 22:57:12]

The CQ bit was checked by maruel@chromium.org

[commit-bot: I haz the power, 2015-04-29 22:57:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1113453007/1

[commit-bot: I haz the power, 2015-04-29 23:01:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-29 23:01:26]

Presubmit check for 1113453007-1 failed and returned exit status 1.

Running presubmit commit checks ...
Checking out rietveld...
Running save-description-on-failure.sh
Running push-basic.sh
Running upstream.sh
Running submit-from-new-dir.sh
Running abandon.sh
Running submodule-merge-test.sh
Running upload-local-tracking-branch.sh
Running hooks.sh
Running post-dcommit-hook-test.sh
Running upload-stale.sh
Running patch.sh
Running basic.sh

** Presubmit ERRORS **
tests/checkout_test.py (38.91s) failed
Cloning into '/tmp/trial4fTMyZ/__main__.GitCheckout.testAll/foo'...
done.
Switched to branch 'master'
Already on 'master'
.sECloning into '/tmp/trial4fTMyZ/__main__.GitCheckout.testProcess/foo'...
done.
....................
======================================================================
ERROR: testMove (__main__.GitCheckout)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/checkout_test.py", line 347, in setUp
    self.enabled = self.FAKE_REPOS.set_up_git()
  File
"/b/infra_internal/commit_queue/workdir/tools/depot_tools/testing_support/fake_repos.py",
line 359, in set_up_git
    self.set_up()
  File
"/b/infra_internal/commit_queue/workdir/tools/depot_tools/testing_support/fake_repos.py",
line 211, in set_up
    self.cleanup_dirt()
  File
"/b/infra_internal/commit_queue/workdir/tools/depot_tools/testing_support/fake_repos.py",
line 229, in cleanup_dirt
    if not self.tear_down_git():
  File
"/b/infra_internal/commit_queue/workdir/tools/depot_tools/testing_support/fake_repos.py",
line 276, in tear_down_git
    wait_for_port_to_free(self.host, self.git_port)
  File
"/b/infra_internal/commit_queue/workdir/tools/depot_tools/testing_support/fake_repos.py",
line 161, in wait_for_port_to_free
    assert False, '%d is still bound' % port
AssertionError: 20000 is still bound

----------------------------------------------------------------------
Ran 23 tests in 38.669s

FAILED (errors=1, skipped=1)


Presubmit checks took 210.0s to calculate.

[ghost stip (do not use), 2015-04-29 23:17:41]

The CQ bit was checked by stip@chromium.org

[commit-bot: I haz the power, 2015-04-29 23:18:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1113453007/1

[commit-bot: I haz the power, 2015-04-29 23:18:24]

Committed patchset #1 (id:1) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=295075