Ask the filename object for the prefix

Library/Homebrew/bottles.rb

@@ -19,11 +19,6 @@ def bottle_file_outdated? f, file
   bottle_ext && bottle_url_ext && bottle_ext != bottle_url_ext
 end
 
-def bottle_suffix revision
-  revision = revision > 0 ? ".#{revision}" : ""
-  ".bottle#{revision}.tar.gz"
-end
-
 def bottle_native_regex
   /(\.#{bottle_tag}\.bottle\.(\d+\.)?tar\.gz)$/o
 end

Library/Homebrew/cmd/bottle.rb

@@ -192,10 +192,7 @@ module Homebrew
     puts output
 
     if ARGV.include? '--rb'
-      bottle_base = filename.to_s.gsub(bottle_suffix(bottle_revision), '')
-      File.open "#{bottle_base}.bottle.rb", 'w' do |file|
-        file.write output
-      end
+      File.open("#{filename.prefix}.bottle.rb", "w") { |file| file.write(output) }
     end
   end
 

Library/Homebrew/software_spec.rb

@@ -124,9 +124,18 @@ class Bottle
     end
 
     def to_s
-      "#{name}-#{version}.#{tag}#{bottle_suffix(revision)}"
+      prefix + suffix
     end
     alias_method :to_str, :to_s
+
+    def prefix
+      "#{name}-#{version}.#{tag}"
+    end
+
+    def suffix
+      s = revision > 0 ? ".#{revision}" : ""
+      ".bottle#{s}.tar.gz"
+    end
   end
 
   extend Forwardable

Library/Homebrew/test/test_bottle_filename.rb

@@ -6,6 +6,12 @@ class BottleFilenameTests < Homebrew::TestCase
     Bottle::Filename.new("foo", "1.0", :tag, revision)
   end
 
+  def test_prefix_suffix
+    assert_equal "foo-1.0.tag", fn(0).prefix
+    assert_equal ".bottle.tar.gz", fn(0).suffix
+    assert_equal ".bottle.1.tar.gz", fn(1).suffix
+  end
+
   def test_to_str
     expected = "foo-1.0.tag.bottle.tar.gz"
     assert_equal expected, fn(0).to_s