Soon after v0.4.1, Geoff unified both kinds of supply lines into one. It now is based off of the Supply meter, not the Infrastructure meter.
As of revision 5138, the content (effects and descriptions) was adjusted to accommodate this new situation.
Unlike the Infrastructure meter, the Supply meter doesn't have a current and max value, so there is no delay, in the appearance of longer supply lines after you acquire the bonus. This is simpler, so let's see if the delayed version is really necessary before we add it back in.
For now Outpost now provide 1 jump supply, and colonies 2 jump supply. The palace adds +1, and other buildings and techs add additional jumps as described. I pulled these numbers out of my hat. It would be easy to think of more complicated formulae, but again let's go with the simplest method until that method is demonstrated to be inadequate.
Note: Techs/Buildings that previously increased the infrastructure meter, if they were presented as supply-line techs now only increase the supply meter. Infrastructure values will now be less, which i didn't think was worth fixing as what to do with infrastructure is under discussion.