TODO

[x] Add tests
[x] For Gentoo system:

    pacapt -Q       => eix -I
    pacapt -Qc <p>  => emerge -p --changelog <p>
    pacapt -Qi <p>  => emerge --info <p>
    pacapt -Ql <p>  => exists("qlist") && qlist <p> || equery files <p>
    pacapt -Qm      => orphan packages, not supported
    pacapt -Qo <f>  => equery belongs <f>
    pacapt -Qp <f>  => not supported, Gentoo virtually has no definition of "package file"

    pacapt -S <p>   => emerge -a <p>
    pacapt -Ss <p>  => eix <p> || emerge --search <p>
    pacapt -Su      => emerge -auND world
    pacapt -Sy      => emerge --sync ; exists("layman") && layman --sync-all
    pacapt -Suy     => emerge --sync ; exists("layman") && layman --sync-all ; emerge -auND world


    pacapt -R <p>   => emerge --depclean <p>

    pacapt -Sc      = clean all distfiles except for installed packages (exact version), those which are less than one month old, bigger than 50MB, or fetch-restricted:
                    => eclean-dist -d -t1m -s50 -f

    pacapt -Scc     => eclean -i distfiles

    -f              => remove "-a"
    -v              => -v
    -w              => --fetchonly