apt-add-repository manpage says this about the command:
REPOSITORY can be either a line that can be added directly to
sources.list(5), in the form ppa:<user>/<ppa-name> for adding Personal
Package Archives, or a distribution component to enable.
In the first form, REPOSITORY will just be appended to
In the second form, ppa:<user>/<ppa-name> will be expanded to the full
deb line of the PPA and added into a new file in the
/etc/apt/sources.list.d/ directory. The GPG public key of the newly
added PPA will also be downloaded and added to apt's keyring.
In the third form, the given distribution component will be enabled for
-r, --remove Remove the specified repository
add-apt-repository just adds and removes lines from
ppa-purge manpage says this:
ppa-purge - disables a PPA and reverts to official packages
This script provides a bash shell script capable of automatically
downgrading all packages in a given PPA back to the ubuntu versions.
You have to run it using root privileges because of the package
ppa-purge will not only remove a PPA, it will also downgrade any packages back to their default versions. This is useful when testing beta or newer versions of software.