Comment 12 for bug 1035273

Thanks for wanting to work on that, yes the debdiff is basically a diff between the unpacked source before and after the change, you have details on https://wiki.ubuntu.com/PackagingGuide/Recipes/Debdiff#Creating_A_Debdiff

Could you also open a new bug against nautilus? Due to a launchpad bug this one can't be used to track a precise upload (it was edited to track and quantal one but the precise line got deleted on the way and can't be added back)

I will review,sponsor the update once it's available