Allow brew versions to work with underspecified formulae

Library/Homebrew/cmd/versions.rb

@@ -77,6 +77,9 @@ class Formula
       rev_list.find{ |sha| version == version_for_sha(sha) }
     end
 
+    IGNORED_EXCEPTIONS = [SyntaxError, TypeError, NameError,
+                          ArgumentError, FormulaSpecificationError]
+
     def version_for_sha sha
       mktemp do
         path = Pathname.new(Pathname.pwd+"#{name}.rb")
@@ -86,7 +89,7 @@ class Formula
         begin
           Object.send(:remove_const, Formula.class_s(name))
           nostdout { Formula.factory(path).version }
-        rescue SyntaxError, TypeError, NameError, ArgumentError => e
+        rescue *IGNORED_EXCEPTIONS => e
           # We rescue these so that we can skip bad versions and
           # continue walking the history
           ohai "#{e} in #{name} at revision #{sha}", e.backtrace if ARGV.debug?

Library/Homebrew/exceptions.rb

@@ -33,6 +33,9 @@ class FormulaValidationError < StandardError
   end
 end
 
+class FormulaSpecificationError < StandardError
+end
+
 class FormulaUnavailableError < RuntimeError
   attr_reader :name
   attr_accessor :dependent

Library/Homebrew/formula.rb

@@ -77,7 +77,7 @@ class Formula
     when @devel && @stable.nil?           then @devel   # devel-only
     when @head && @stable.nil?            then @head    # head-only
     else
-      raise "Formulae require at least a URL"
+      raise FormulaSpecificationError, "formulae require at least a URL"
     end
   end
 

Library/Homebrew/test/test_formula_validation.rb

@@ -78,7 +78,7 @@ class FormulaValidationTests < Test::Unit::TestCase
   end
 
   def test_empty_formula_invalid
-    e = assert_raises(RuntimeError) { formula {} }
+    e = assert_raises(FormulaSpecificationError) { formula {} }
-    assert_equal "Formulae require at least a URL", e.message
+    assert_equal "formulae require at least a URL", e.message
   end
 end