The Changelog of Karmic read so :


software-properties (0.75) karmic; urgency=low

* new helper script "add-apt-repository" that can be used to
enable a repository from the commandline. Useful for e.g.
'add-apt-repository ppa:gnome-desktop'
* fix error in auto-upgrade settings when
dpkg-reconfigure unattended-upgrades was used (LP: #387704)
* po/zh_TW.po:
- updated, thanks to Roy Chan (LP: #365040)
* softwareproperties/kde/SoftwarePropertiesKDE.py:
- do not error on cancel (LP: #364288)
- use the SUDO_USER home instead of /root (if available)
(LP: #364197)
- add utf8() function and replace the custom converts to it
(hopefully fixes LP: #362188)
- disable "Find best server" for now, the threading crashing
KDE
* softwareproperties/gtk/DialogCacheOutdated.py:
- fix incorrect wait on synaptic (LP: #357617, LP: #349639)
* softwareproperties/SoftwareProperties.py:
- check/ensure apt daily cron job is executable (LP: #390319)

-- Michael Vogt Tue, 14 Jul 2009 16:54:38 +0200

A sweet helper script to add repo to /etc/apt/source.list along with gpg key import.

What we were doing in the earlier versions :
{As an Example}

Step 1: On the PPA's overview page you'll see the PPA's OpenPGP key id. It'll look something like this: 1024/12345678. Copy it, or make a note of, the portion after the slash, e.g: 12345678.

Step 2: Open your terminal and enter:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 12345678

Replace 12345678 with the key id you copied in step 1.

Step 3: Finally, tell Ubuntu to re-load the details of each software archive it knows about:

sudo apt-get update

Now in karmic with the new helper script :

add-apt-repository ppa:ppa_name

That's it this adds the ppa to source.list and also imports the keys.