Stick this in a library file...

file_provider_copy.rb

class Chef
  class Provider
    class File
      class Copy << Chef::Provider::File
       
        def compare_content
          checksum(@current_resource.path) == checksum(@new_resource.content)
        end

        def set_content
          unless compare_content
            backup @new_resource.path if ::File.exists?(@new_resource.path)
            ::File.cp_r(@new_resource.content, @new_resource.path)
            Chef::Log.info("#{@new_resource.content} copied to #{@new_resource.path}")
            @new_resource.updated_by_last_action(true)
          end
        end
      end
    end
  end
end

recipe.rb

file "/tmp/foo" do
  content "/tmp/bar"
  provider Chef::Provider::File::Copy
end

Couple of typos:

--- file_provider_copy.rb.orig 2011-09-09 10:50:50.000000000 +0100
+++ file_provider_copy.rb 2011-09-09 10:34:03.000000000 +0100
@@ -3,7 +3,7 @@
class Chef
class Provider
class File

•  class Copy << Chef::Provider::File
  

•  class Copy < Chef::Provider::File
  
   def compare_content
     checksum(@current_resource.path) == checksum(@new_resource.content)
  

  @@ -12,7 +12,7 @@
  def set_content
  unless compare_content
  backup @new_resource.path if ::File.exists?(@new_resource.path)

•        ::File.cp_r(@new_resource.content, @new_resource.path)
  

•        ::FileUtils.cp_r(@new_resource.content, @new_resource.path)
       Chef::Log.info("#{@new_resource.content} copied to #{@new_resource.path}")
       @new_resource.updated_by_last_action(true)
     end
  

This works only if the file exists already, otherwise the chef File provider uses the content directly ..
What is the best fix for this ?

Snipet from the original code :

unless ::File.exists?(@new_resource.path)
      Chef::Log.info("Creating #{@new_resource} at #{@new_resource.path}")
        ::File.open(@new_resource.path, "w+") {|f| f.write @new_resource.content }
        @new_resource.updated_by_last_action(true)
      else
        set_content unless @new_resource.content.nil?

A safer solution would be to add a new attribute instead of re-using content for this.