Pathname: add cp_path_sub method.

This method allows copying a file to a new location by performing a
substitution on the pathname.

Library/Homebrew/extend/pathname.rb

@@ -115,6 +115,27 @@ class Pathname
     return dst
   end
 
+  def cp_path_sub pattern, replacement
+    raise "#{self} does not exist" unless self.exist?
+
+    src = self.to_s
+    dst = src.sub(pattern, replacement)
+    raise "#{src} is the same file as #{dst}" if src == dst
+
+    dst_path = Pathname.new dst
+
+    if self.directory?
+      dst_path.mkpath
+      return
+    end
+
+    dst_path.dirname.mkpath
+
+    dst = yield(src, dst) if block_given?
+
+    FileUtils.cp(src, dst)
+  end
+
   # extended to support common double extensions
   alias extname_old extname
   def extname(path=to_s)

Library/Homebrew/install_renamed.rb

@@ -6,6 +6,12 @@ module InstallRenamed
     end
   end
 
+  def cp_path_sub pattern, replacement
+    super do |src, dst|
+      append_default_if_different(src, dst)
+    end
+  end
+
   private
 
   def append_default_if_different src, dst