Fix installing a local bottle from source

Factor Utils::Bottles.formula_contents out of BottleLoader.

Library/Homebrew/formula_installer.rb

@@ -308,7 +308,12 @@ class FormulaInstaller
       clean
 
       # Store the formula used to build the keg in the keg.
-      s = formula.path.read.gsub(/  bottle do.+?end\n\n?/m, "")
+      formula_contents = if formula.local_bottle_path
+        Utils::Bottles.formula_contents formula.local_bottle_path, name: formula.name
+      else
+        formula.path.read
+      end
+      s = formula_contents.gsub(/  bottle do.+?end\n\n?/m, "")
       brew_prefix = formula.prefix/".brew"
       brew_prefix.mkdir
       Pathname(brew_prefix/"#{formula.name}.rb").atomic_write(s)

Library/Homebrew/utils/bottles.rb

@@ -54,6 +54,15 @@ module Utils
       def resolve_version(bottle_file)
         PkgVersion.parse receipt_path(bottle_file).split("/")[1]
       end
+
+      def formula_contents(bottle_file,
+          name: resolve_formula_names(bottle_file)[0])
+        bottle_version = resolve_version bottle_file
+        formula_path = "#{name}/#{bottle_version}/.brew/#{name}.rb"
+        contents = Utils.popen_read "tar", "-xOzf", bottle_file, formula_path
+        raise BottleFormulaUnavailableError.new(bottle_file, formula_path) unless $CHILD_STATUS.success?
+        contents
+      end
     end
 
     class Bintray