It's very basic, only subcommands.

If this would evolve, generation of _gclient should be automized (like a separate command
or some other tool.)

Review URL: http://codereview.chromium.org/546069

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@36521 0039d316-1c4b-4281-b951-d872f2087c98