Support deb-get

[Zahrun]

I want to suggest a new step

Which tool is this about? Where is its repository?

deb-get gives apt-get functionality for .debs published in 3rd party repositories or via direct download https://github.com/wimpysworld/deb-get

Which operating systems are supported by this tool?

Linux Ubuntu and derivative distributions.

What should Topgrade do to figure out if the tool needs to be invoked?

Check if /bin/deb-get exists

Which exact commands should Topgrade run?

sudo deb-get update
sudo deb-get upgrade