When packaging new backport versions, I diff the old Debian package with the old backport package to extract the changes I did there, and then apply this patch to the new version. There is always a reject in debian/changelog because the topmost bpo entry won't apply cleanly to the new changelog. To fix this, I invoke "vi debian/changelog*" and manually copy the rejected hunk.

Unfortunately, I regularly end up copying it from debian/changelog.rej (buffer 3) into debian/changelog.orig (buffer 2) instead of debian/changelog (buffer 1). Here's the fix in my .vimrc:

" Prevent accidental editing of patch .orig files
autocmd BufRead *.orig set readonly