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GitHub User: corejh
for anyone curious, my solution to this problem was to drop the deep_merge approach entirely. Instead of storing all the model information in the session_params, I just created the model in the "first step" then called update_attributes on it in the following steps, effectively "saving" it between steps. This isn't exactly the same behavior shown in this cast, but it's actually better in my case.
Can anyone point me in the right direction getting this to work with file uploading? I've tried just sort of mashing file uploading in there, but you can't store files in a session variable (you get type error, can't dump file).