Git repositories on github

After some initial issues the git conversion seems to be stable now. Both src and https://github.com/jsonn/pkgsrc can be found on github.

Fun fact about git: pushing trunk from src alone and the other refs with push -all afterwards requires 50% more space than doing the push -all in first place.

One issue remains. I can't do incremental exports from fossil to git, because git can't find objects it has imported earlier. I'm not the first person to experience this, but it seems no one cares enough to fix it.