ssh://test@example.com wasn't being parsed correctly for revinfo.

Fixed by factoring out all code which splits url into a base_url
and revision.

Review URL: http://codereview.chromium.org/391048

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@31910 0039d316-1c4b-4281-b951-d872f2087c98