Add the cache_only configuration option

lib/carrierwave/uploader/configuration.rb

@@ -38,6 +38,7 @@ module Configuration
         add_config :validate_processing
         add_config :validate_download
         add_config :mount_on
+        add_config :cache_only
 
         # set default values
         reset_config

lib/carrierwave/uploader/store.rb

@@ -54,7 +54,7 @@ def store_path(for_file=filename)
       #
       def store!(new_file=nil)
         cache!(new_file) if new_file && ((@cache_id != parent_cache_id) || @cache_id.nil?)
-        if @file and @cache_id
+        if !cache_only and @file and @cache_id
           with_callbacks(:store, new_file) do
             new_file = storage.store!(@file)
             if delete_tmp_file_after_storage

spec/uploader/store_spec.rb

@@ -102,6 +102,35 @@
       @uploader.store!
     end
 
+    context "with the cache_only option set to true" do
+      before do
+        @uploader_class.cache_only = true
+      end
+
+      it "should not instruct the storage engine to store the file" do
+        @uploader.cache!(@file)
+        @storage.should_not_receive(:store!)
+        @uploader.store!
+      end
+
+      it "should still be cached" do
+        @uploader.store!(@file)
+        @uploader.should be_cached
+      end
+
+      it "should not reset the cache_name" do
+        @uploader.cache!(@file)
+        @uploader.store!
+        @uploader.cache_name.should_not be_nil
+      end
+
+      it "should not delete the old file" do
+        @uploader.cache!(@file)
+        @uploader.file.should_not_receive(:delete)
+        @uploader.store!
+      end
+    end
+
     context "with the delete_tmp_file_after_storage option set to false" do
       before do
         @uploader_class.delete_tmp_file_after_storage = false