Jasig/cas — pull request #277 by serac (2013-06-19 21:24:23+00:00)
Title: CAS-1219 Perform TGT Validity Check at Start of Login Flow

Replace boolean ticket check state with a tristate action that checks the flow request context and ticket registry for TGT validity and returns one of the following events:

1. notExists
2. invalid
3. valid

In the second case the browser cookie is deleted and the ticket is deleted from the registry (if found).