Add .files support for pacsync

[AladW]

The command

pacsync myrepo

allows to retrieve .db files for a given repo, but it does not retrieve .files. Since pacman -Fy (like pacman -Sy) applies to all repositories only, it seems useful for pacsync to also support this.

Alternatively, a new command could be added which operates on .files databases (like pacman -F).

[andrewgregory]

--dbext=.files ?

[AladW]

Good point!