Add 'keep_old_files' option.

From https://github.com/pcreux/paperclip/commit/52374958ef83f1641cf008aead27c23b25fb842d

Conflicts:

	lib/paperclip/attachment.rb

lib/paperclip.rb

@@ -266,6 +266,9 @@ module Paperclip
     #     has_attached_file :avatar, :styles => { :normal => "100x100#" },
     #                       :default_style => :normal
     #     user.avatar.url # => "/avatars/23/normal_me.png"
+    # * +keep_old_files+: Keep the existing attachment files (original + resized) from
+    #   being automatically deleted when an attachment is cleared or updated.
+    #   Defaults to +false+.#
     # * +whiny+: Will raise an error if Paperclip cannot post_process an uploaded file due
     #   to a command line error. This will override the global setting for this attachment.
     #   Defaults to true. This option used to be called :whiny_thumbanils, but this is

lib/paperclip/attachment.rb

@@ -208,7 +208,7 @@ module Paperclip
     # Saves the file, if there are no errors. If there are, it flushes them to
     # the instance's errors and returns false, cancelling the save.
     def save
-      flush_deletes
+      flush_deletes unless @options[:keep_old_files]
       flush_writes
       @dirty = false
       true

test/attachment_test.rb

@@ -893,6 +893,41 @@ class AttachmentTest < Test::Unit::TestCase
                 @attachment.destroy
                 @existing_names.each{|f| assert ! File.exists?(f) }
               end
+
+              context "when keeping old files" do
+                setup do
+                  @attachment.options[:keep_old_files] = true
+                end
+
+                should "keep the files after assigning nil" do
+                  @attachment.expects(:instance_write).with(:file_name, nil)
+                  @attachment.expects(:instance_write).with(:content_type, nil)
+                  @attachment.expects(:instance_write).with(:file_size, nil)
+                  @attachment.expects(:instance_write).with(:updated_at, nil)
+                  @attachment.assign nil
+                  @attachment.save
+                  @existing_names.each{|f| assert File.exists?(f) }
+                end
+
+                should "keep the files when you call #clear and #save" do
+                  @attachment.expects(:instance_write).with(:file_name, nil)
+                  @attachment.expects(:instance_write).with(:content_type, nil)
+                  @attachment.expects(:instance_write).with(:file_size, nil)
+                  @attachment.expects(:instance_write).with(:updated_at, nil)
+                  @attachment.clear
+                  @attachment.save
+                  @existing_names.each{|f| assert File.exists?(f) }
+                end
+
+                should "keep the files when you call #delete" do
+                  @attachment.expects(:instance_write).with(:file_name, nil)
+                  @attachment.expects(:instance_write).with(:content_type, nil)
+                  @attachment.expects(:instance_write).with(:file_size, nil)
+                  @attachment.expects(:instance_write).with(:updated_at, nil)
+                  @attachment.destroy
+                  @existing_names.each{|f| assert File.exists?(f) }
+                end
+              end
             end
           end
         end