Fix 'brew install f' for already-installed brews.

Library/Homebrew/exceptions.rb

@@ -35,10 +35,7 @@ module Homebrew
   class InstallationError < RuntimeError
     attr :formula
 
-    def initialize formula
-      @formula = formula
-    end
-    def initialize formula, message
+    def initialize formula, message=""
       super message
       @formula = formula
     end

Library/Homebrew/formula_installer.rb

@@ -13,7 +13,8 @@ class FormulaInstaller
   def go
     if @f.installed? and not ARGV.force?
       raise FormulaAlreadyInstalledError, @f
-    else
+    end
+
     unless ignore_deps
       @f.recursive_deps.each do |dep|
         FormulaInstaller.install_formula dep unless dep.installed?
@@ -22,7 +23,6 @@ class FormulaInstaller
     end
     FormulaInstaller.install_formula @f
   end
-  end
 
   def self.check_external_deps f
     [:ruby, :python, :perl, :jruby].each do |type|