initializing portmaster's local-packagedir

[perryh at pluto.rain.com]

Starting with a single directory containing a few hundred packages
(.tbz files), how would I go about converting it into the sort of
repository which portmaster could use as its --local-packagedir?

I suppose the first step would be something along the lines of

  mkdir .all
  mv *.tbz .all
  mv .all All

but how do I figure out which packages go in each of the category
directories and in Latest?