You can clone with
sudo apt-get install mercurial
sudo apt-get build-dep vim
# switch to appropriate directory (I use ~/local/ubuntu-pkgs/vim)
hg clone http://hg.debian.org/hg/pkg-vim/vim
hg checkout unstable
# there are your debs
# switch to checkout directory
When vim-lesstif was removed, some of the files were left in my working copy, which I had to delete before the build would work.
Used to have -i -I options for dpkg-buildpackage, but I'm not sure why....