Don't lie about upgrading up-to-date formulae

Usually, the "foo-version already installed" error is printed by
FormulaInstaller. However, if an up-to-date formula that has outdated
deps is passed on the command line, we proceed to upgrade the deps and
then print a message saying that the formulae given on the command line
is already installed.

Catch this earlier, when the outdated list is being populated, print an
appropriate message, and skip the up-to-date formula.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Homebrew/cmd/upgrade.rb

@@ -21,7 +21,9 @@ module Homebrew extend self
       Homebrew.outdated_brews
     else
       ARGV.formulae.select do |f|
-        unless f.rack.exist? and not f.rack.children.empty?
+        if f.installed?
+          onoe "#{f}-#{f.installed_version} already installed"
+        elsif not f.rack.exist? or f.rack.children.empty?
           onoe "#{f} not installed"
         else
           true

Library/Homebrew/formula.rb

@@ -105,6 +105,11 @@ class Formula
     end
   end
 
+  def installed_version
+    require 'keg'
+    Keg.new(installed_prefix).version
+  end
+
   def prefix
     validate_variable :name
     validate_variable :version

Library/Homebrew/formula_installer.rb

@@ -24,8 +24,7 @@ class FormulaInstaller
 
   def check_install_sanity
     if f.installed?
-      keg = Keg.new(f.installed_prefix)
-      raise CannotInstallFormulaError, "#{f}-#{keg.version} already installed"
+      raise CannotInstallFormulaError, "#{f}-#{f.installed_version} already installed"
     end
 
     # Building head-only without --HEAD is an error