Stop warning about CLT w/o Xcode

Also made the latest_versions checks smarter. Hopefully correct too.

Library/Homebrew/cmd/doctor.rb

@@ -206,49 +206,27 @@ end
 
 def check_for_latest_xcode
   if not MacOS::Xcode.installed?
-    # no Xcode, now it depends on the OS X version...
-    if MacOS.version >= 10.7 then
+    if MacOS.version >= 10.7
       if not MacOS::CLT.installed?
-        return <<-EOS.undent
-          No Xcode version found!
-          No compiler found in /usr/bin!
-
-          To fix this, either:
-          - Install the "Command Line Tools for Xcode" from http://connect.apple.com/
-            Homebrew does not require all of Xcode, you only need the CLI tools package!
-            (However, you need a (free) Apple Developer ID.)
-          - Install Xcode from the Mac App Store. (Normal Apple ID is sufficient, here)
+        <<-EOS.undent
+        No developer tools installed
+        You should install the Command Line Tools: http://connect.apple.com
         EOS
-      else
-        return <<-EOS.undent
-          Experimental support for using the "Command Line Tools" without Xcode.
-          Some formulae need Xcode to be installed (for the Frameworks not in the CLT.)
+      elsif not MacOS::CLT.latest_version?
+        <<-EOS.undent
+        A newer Command Line Tools for Xcode release is avaliable
+        You should install the latest version from: http://connect.apple.com
         EOS
       end
     else
-      # older Mac systems should just install their old Xcode. We don't advertize the CLT.
-      return <<-EOS.undent
-        We couldn't detect any version of Xcode.
-        If you downloaded Xcode from the App Store, you may need to run the installer.
+      <<-EOS.undent
+      Xcode not installed
+      Most stuff needs Xcode to build: http://developer.apple.com/xcode/
       EOS
     end
-  end
-
-  latest_xcode = case MacOS.version
-    when 10.5 then "3.1.4"
-    when 10.6 then "3.2.6"
-    when 10.7 then "4.3.3"
-    when 10.8 then "4.4"
-    else nil
-  end
-  if latest_xcode.nil?
-    return <<-EOS.undent
-    Not sure what version of Xcode is the latest for OS X #{MacOS.version}.
-    EOS
-  end
-  if MacOS::Xcode.installed? and MacOS::Xcode.version < latest_xcode then <<-EOS.undent
-    You have Xcode-#{MacOS::Xcode.version}, which is outdated.
-    Please install Xcode #{latest_xcode}.
+  elsif MacOS::Xcode.version < MacOS::Xcode.latest_version then <<-EOS.undent
+    Your Xcode (#{MacOS::Xcode.version}) is outdated
+    Please install Xcode #{MacOS::Xcode.latest_version}.
     EOS
   end
 end

Library/Homebrew/macos/xcode.rb

@@ -16,6 +16,19 @@ module MacOS::Xcode extend self
     folder == "/"
   end
 
+  def latest_version
+    case MacOS.version
+      when 10.5 then "3.1.4"
+      when 10.6 then "3.2.6"
+    else
+      if MacOS.version >= 10.7
+        "4.4.1"
+      else
+        raise "Mac OS X `#{MacOS.version}' is invalid"
+      end
+    end
+  end
+
   def prefix
     @prefix ||= begin
       path = Pathname.new folder
@@ -144,6 +157,11 @@ module MacOS::CLT extend self
     MacOS.dev_tools_path == Pathname.new("/usr/bin")
   end
 
+  def latest_version?
+    `/usr/bin/clang -v` =~ %r{tags/Apple/clang-(\d+).(\d+).(\d+)}
+    $1 >= 421 and $3 >= 57
+  end
+
   def version
     # Version string (a pretty damn long one) of the CLT package.
     # Note, that different ways to install the CLTs lead to different