Allow resource fetching

Closes Homebrew/homebrew#20047.

Library/Homebrew/cmd/fetch.rb

@@ -16,14 +16,36 @@ module Homebrew extend self
     end
 
     puts "Fetching: #{bucket * ', '}" if bucket.size > 1
-    bucket.each { |f| fetch_formula(f) }
+    bucket.each do |f|
+      fetch_formula(f)
+      f.resources.each do |r|
+        fetch_resource(r)
+      end
+    end
   end
 
   def already_fetched? f
     f.cached_download.exist?
   end
 
+  def fetch_resource r
+    puts "Resource: #{r.name}"
+    fetch_fetchable r
+  rescue ChecksumMismatchError => e
+    Homebrew.failed = true
+    opoo "Resource #{r.name} reports different #{e.hash_type}: #{e.expected}"
+  end
+
   def fetch_formula f
+    fetch_fetchable f
+  rescue ChecksumMismatchError => e
+    Homebrew.failed = true
+    opoo "Formula reports different #{e.hash_type}: #{e.expected}"
+  end
+
+  private
+
+  def fetch_fetchable f
     f.cached_download.rmtree if already_fetched?(f) && ARGV.force?
     download = f.fetch
 
@@ -33,8 +55,5 @@ module Homebrew extend self
     puts Checksum::TYPES.map { |t| "#{t.to_s.upcase}: #{download.send(t)}" }
 
     f.verify_download_integrity(download)
-  rescue ChecksumMismatchError => e
-    Homebrew.failed = true
-    opoo "Formula reports different #{e.hash_type}: #{e.expected}"
   end
 end