Oh well, I have come to think of a problem: if one builds an old
version of the docs, then the tip symlink will point to that. And so
the "latest" documentation will suddenly be some old version.

We could disable the push botton on the buildbot pages -- so far I
have only used it when I changed something in the buildbot settings
and had to debug it. But for everyday development I have never had to
force a build.

Or we could let something else than the buildslaves make the link. A
hook in the repository could create it whenever stuff is pushed into
it. But that is somewhat brittle, for what if the build fails and the
symlink points to nothing?

By the way: I could have created a hook in the repository which would
take care of building the docs, but I felt that it was nicer to
offload it to somewhere else than the DreamHost machine. This has the
advantage that I wont have to wait for everything to build when
pushing. But the complexity might not be worth it...