I (thought that I) needed to add a ppa repo to a crunchbang, (debian) install:
(N.B. "raring" is the ubuntu version that matched the version of debian that I was using) so I did:
sudo su -
# you can call the file anything that you want, but it has to end with .list to be a valid for apt-get
echo 'deb http://ppa.launchpad.net/yannubuntu/boot-repair/ubuntu/ raring main'>> /etc/apt/sources.list.d/boot-repair.list
# get the keys for that repo so that apt can verify the signed .deb files
apt-key add Release.gpg
#gpg --search-keys 60D8DA0B
Most of this is explained on the boot-repair page, (though in the end testdisk and then Gparted were what I actually needed to restore a lost partition and a corrupted MBR.) This probably isn't The Debian way (TM) but it worked for me.
Some debian repos are the "old style" and then you only need a line like:
deb http://repo.alexx.net/apt/ /
# the trailing slash needs to be there
add-apt-repository is good if you have it, but that seems to be more ubuntu.