[3/3] cmd: implemented && and || functionality (try 2)

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=11295

Your paranoid android.


=== build (build) ===
Patch failed to apply