Teach fetch to download patches

Library/Homebrew/cmd/fetch.rb

@@ -21,9 +21,8 @@ module Homebrew extend self
         fetch_formula(f.bottle)
       else
         fetch_formula(f)
-        f.resources.each do |r|
+        f.resources.each { |r| fetch_resource(r) }
-          fetch_resource(r)
+        f.patchlist.select(&:external?).each { |p| fetch_patch(p) }
-        end
       end
     end
   end
@@ -51,6 +50,13 @@ module Homebrew extend self
     opoo "Formula reports different #{e.hash_type}: #{e.expected}"
   end
 
+  def fetch_patch p
+    fetch_fetchable p
+  rescue ChecksumMismatchError => e
+    Homebrew.failed = true
+    opoo "Patch reports different #{e.hash_type}: #{e.expected}"
+  end
+
   private
 
   def retry_fetch? f

Library/Homebrew/formula.rb

@@ -117,6 +117,10 @@ class Formula
     active_spec.clear_cache
   end
 
+  def patchlist
+    active_spec.patches
+  end
+
   # if the dir is there, but it's empty we consider it not installed
   def installed?
     (dir = installed_prefix).directory? && dir.children.length > 0

Library/Homebrew/patch.rb

@@ -1,6 +1,7 @@
 require 'resource'
 require 'stringio'
 require 'erb'
+require 'forwardable'
 
 class Patch
   def self.create(strip, io=nil, &block)
@@ -80,8 +81,13 @@ class IOPatch < Patch
 end
 
 class ExternalPatch < Patch
+  extend Forwardable
+
   attr_reader :resource, :strip
 
+  def_delegators :@resource, :fetch, :verify_download_integrity,
+    :cached_download, :clear_cache
+
   def initialize(strip, &block)
     @strip    = strip
     @resource = Resource.new(&block)