allow --rand to take a string. Make full name --randomize.

README

@@ -92,9 +92,11 @@ closer to saying what you mean.
   % drake --rand[=SEED]
 
 This will randomize the order of sibling prerequisites for each task.
-When given the optional SEED integer, it will call
-<tt>srand(SEED)</tt> to produce the same permutation each time.  The
-randomize option also disables +multitask+.
+When given the optional SEED string, it will call
+<tt>srand(SEED.hash)</tt> to produce the same permutation each time
+(String#hash produces the integer which is the seed).  The randomize
+option also disables +multitask+, making it a regular unthreaded
++task+.
 
 Though this option may produce an error due to an unspecified
 dependency, at least it will be an error which is exactly the same on

lib/rake.rb

@@ -2282,12 +2282,12 @@ def standard_rake_options
         ['--threads', '-j N', "Specifies the number of threads to run simultaneously.",
           lambda { |value| self.num_threads = value.to_i }
         ],
-        ['--rand[=SEED]', "Randomize task prerequisite orders",
+        ['--randomize[=SEED]', "Randomize task prerequisite orders",
           lambda { |value|
             MultiTask.class_eval { remove_method(:invoke_prerequisites) }
             options.randomize = true
             if value
-              srand(value.to_i)
+              srand(value.hash)
             end
           }
         ],