Make installation of software-properties optional

[bodepd]

To simplify configuration of package installs on
Ubuntu, I frequently do the following:

Apt::Source<||> -> Package<||>

To ensure that apt source configuration occurrs before
package installation. Having the ppas install software
properties breaks this pattern because it means that
the apt-get update must be run both before and after
software properties resulting in a dependency cycle.

For my purposes, the value of being able to stage
apt operations before packages is significannt enough
that I just ensure that software properties in installed
as a part of my base image.

According to the following issue, this looks like it has
been resolved as of 14.04 (that this library is installed
by default)

https://bugs.launchpad.net/ubuntu/+source/ubuntu-meta/+bug/439566

[daenney]

Hmm, I can see this working and is a nicer solution to the ugly hacks we've had proposed before. Can we confirm that on 14.04 we get python-software-properties or whatever the heck that package is called now by default and flip the default accordingly through params.pp?

People should still be able to override it so when they provide it in their 'base' image on a 12.10 machine we don't get upset about it but it would make the whole thing more sane by default and confuse new users even less.

[bodepd]

@sorenh can you help point me to something that confirms that is software-properties-common is installed as a part of 14.04?

[sorenisanerd]

I'm not quite sure what kind of evidence you need.

$ dpkg -S `which add-apt-repository`
software-properties-common: /usr/bin/add-apt-repository
$ apt-cache show software-properties-common | grep ^Task:
Task: ubuntu-desktop, ubuntu-usb, cloud-image, server, kubuntu-desktop, kubuntu-full, kubuntu-active, kubuntu-active-desktop, kubuntu-active-full, kubuntu-active, edubuntu-desktop, edubuntu-usb, xubuntu-desktop, mythbuntu-frontend, mythbuntu-desktop, mythbuntu-backend-slave, mythbuntu-backend-master, mythbuntu-backend-master, lubuntu-desktop, ubuntustudio-desktop, ubuntu-gnome-desktop

Those tasks are used when installing various types of systems. *-desktop, cloud-image and server cover pretty much every real use case.

Nevertheless, removing software-properties-common is perfectly possible, so there's no guarantee it's available. It'd be quite unusual, though.

[bodepd]

thanks @sorenh, that is exactly the level of detail I was looking for.

[WolverineFan]

For what it's worth, on LinuxMint 17.1 (which is derived from Ubuntu 14.04 Trusty):

# dpkg-query --search /usr/bin/add-apt-repository
mintsources: /usr/bin/add-apt-repository
# dpkg-query --list software-properties-common
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                    Version                  Architecture             Description
+++-=======================================-========================-========================-===================================================================================
un  software-properties-common              <none>                   <none>                   (no description available)

And their hacked version of add-apt-repository sucks by the way. I lobbied against removing the software-properties-common package but lost.

[underscorgan]

@bodepd thanks for the contribution! Can you update the README with information on the new parameter?

[underscorgan]

@bodepd thanks for the contribution! We ended up implementing that for our work in apt/next so I pulled in the work we had done there in #462.