Use Formula.path

Library/Homebrew/cmd/edit.rb

@@ -30,7 +30,7 @@ module Homebrew extend self
         if name.include? '/'
           Pathname.new(name)
         else
-          HOMEBREW_REPOSITORY+"Library/Formula/#{name}.rb"
+          Formula.path(name)
         end
       end
       unless ARGV.force?

Library/Homebrew/cmd/install.rb

@@ -25,7 +25,7 @@ module Homebrew extend self
 
     ARGV.named.each do |name|
       # if a formula has been tapped ignore the blacklisting
-      if not File.file? HOMEBREW_REPOSITORY/"Library/Formula/#{name}.rb"
+      unless Formula.path(name).file?
         msg = blacklisted? name
         raise "No available formula for #{name}\n#{msg}" if msg
       end

Library/Homebrew/cmd/log.rb

@@ -8,7 +8,7 @@ module Homebrew extend self
         path = ARGV.formulae.first.path.realpath
       rescue FormulaUnavailableError
         # Maybe the formula was deleted
-        path = HOMEBREW_REPOSITORY/"Library/Formula/#{ARGV.named.first}.rb"
+        path = Formula.path(ARGV.named.first)
       end
       cd path.dirname # supports taps
       exec "git", "log", *ARGV.options_only + ["--", path]

Library/Homebrew/formula.rb

@@ -403,7 +403,7 @@ class Formula
     end
 
     # test if the name is a core formula
-    formula_with_that_name = Pathname.new("#{HOMEBREW_LIBRARY}/Formula/#{name}.rb")
+    formula_with_that_name = Formula.path(name)
     if formula_with_that_name.file? and formula_with_that_name.readable?
       return name
     end