Say I don't know what all the dependencies are until I've already  
begun executing tasks?  To what extent can I add new tasks and  
dependencies on the fly?   At first I thought that adding tasks  
during task execution didn't seem to be a safe thing to do.  Then I  
made a few toy examples that seem to confirm this.  So I started  
thinking that I need to have Rake call Rake, which seemed a bit  
clumsy.    But then I read this discussion mentioned by Jim Weirich  
that  seemed to imply that I ought to be able to make a single rake  
file do the job (http://markmail.org/message/jttfqf6wstvgahec#query: 
+page:1+mid:zlc5qjj5r6abfcse+state:results).   But I couldn't find  
any details on how to accomplish this.  Are there better ways of  
handing this problem that don't involve multiple rake files and rake  
calling rake?