[minor/trivial] --fetch requires --install to work

[yoshi314]

paludis --fetch glibc Usage error: you should specify exactly one action

paludis -f glibc Usage error: you should specify exactly one action

paludis -if glibc works

i think it is a bit misleading, since -fi just fetches the distfiles, so -i seems unused.

perhaps it would be more logical if -f could be used to just fetch the distfiles, and -fi/-if to fetch them and afterwards start the building (could be useful with installing multiple packages)

[ciaranm]

This is, at present, considered a feature. --install is the action, --fetch is an option to the action.