How to prevent image files being duplicated while importing nodes with the Feeds module? I have a large catalog import where the items often refer to a single common image (such as "brand_logo"). When I import the images via CSV parser, if the item refers to the same image file, an incremented duplicate is created.

Example: Using the example files supplied with the module, I modified 2 books to use the same image file, which are imported to files/field/image/ as 51JQbhO0MmL.jpg and 51JQbhO0MmL_0.jpg.

This causes the images directory to balloon to 20 times the size it should be (lots of shared images).

Honestly, what I would prefer to do is to upload the images to the site separately (manually, via FTP etc.) and just import the links to the images, but I haven't figured that one out either.

(The data (files) is not being replicated, just the images are replicated.)
I found a solution to this. What you need to do is to install the Media Feeds module.  

In your CSV file there is a column called e.g. image and reference the image using public://myimage.png.

Then in your mapping delete the original image mapping and create a new image mapping. When you do this you will have a new option for the image mapping.  Make sure you set the target configuration to "Source is exactly the filename".  

No more duplicated images.