Dependency policy according to selected package manager

[PeterDaveHello]

aptitude & apt-get uses different policies to decide the dependencies, apt-fast uses apt-get's to decide, if we let apt-fast to use aptitude, it may miss some files or download useless files.

[chrstphrchvz]

The same happens with apt: apt upgrade will install new packages, whereas apt-get upgrade will not. However, apt can list the needed uris for apt-fast.