Hi!

This is a repost of the MR in salsa, to improve the general handling for
third-party commands, and performs a full canonical move to /usr, which
will be eventually needed anyway (once the dh_movetousr hack goes away).

But if there are intentions to backport this version as is then the full
move will not be doable right now I guess.

Patches attached.

Thanks,
Guillem