Relative URLs for linking to other items

I have an image item which is an that is a detail of another image item. I'd like to link from the detail to the full image. Because my site is on a development server and since the base URL is going to change when the site goes live, I'm trying to use relative URLs.

The URL for the detail is http://omeka.home.bju.edu/items/show/55.

The URL for the full image is
http://omeka.home.bju.edu/items/show/56.

So, in the description of detail, I put a link to ../../items/show/56. (Note: I can't just do ../show/56 because the description also shows up on the collection page, which is located at http://omeka.home.bju.edu/collections/show/5.)

The trouble is that Omeka changes the relative URL from ../../items/show/56 to ../show/56. It makes that change whether I'm using the TinyMCE editor or editing the HTML directly. Anyway around this?

On second thought, Omeka might be smarter than I thought. If I enter the absolute URL http://omeka.home.bju.edu/items/show/56 and save the item, Omeka changes it to the relative URL ../../../items/show/56. I guess that's exactly what I need.