Automatically generate help and enforce stricter argument parsing.
Stops from throwing an exception when run outside a subversion checkout.
Fixed gcl lint.

Review URL: http://codereview.chromium.org/2301003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@48386 0039d316-1c4b-4281-b951-d872f2087c98