It is possible to use buildbot to cause the building and uploading of packages,
triggered by pushes into the central repository.  The typical practice is to
write your "build and upload" script in the scripting language of your choice,
e.g. GNU make, bash, Python, or Haskell, and then have buildbot invoke your
"build and upload" script, after a patch has been pushed to the repository, and
after all unit tests passed.  You can of course also configure it to build and
upload packages even if all the unit tests on all the builders didn't pass.

Here is an example buildbot configuration, from the allmydata.org buildbot,
which triggers the build of debian packages on various buildslaves only if the
unit tests passed on all of the debian builders:

debian_platforms = ["etch", "edgy", "feisty", "gutsy", "hardy"]
s_full_debbable = Scheduler(name="full-debbable",
                                branch=None,
                                treeStableTimer=30,
                                builderNames=debian_platforms,
                                )
c['schedulers'].append(s_full_debbable)
debian_package_builders = ["deb-"+name
                               for name in debian_platforms]
s_debs = Dependent("debs", s_full_debbable, debian_package_builders)
c['schedulers'].append(s_debs)

Hi Zooko, what's the status? I recall that you put the infrastructure in place, 
are there still reasons to keep this ticket open?

The set up of the infrastructure is pretty good.  We could choose to make a goal
of having automated build and upload of binaries for all supported platforms and
then to have those binaries copied over onto the binaries page of the wiki.  If
we accomplished that goal then for those platforms there would always be an
up-to-date binary available.  Currently we have Linux, Mac, Windows, OpenBSD,
and Solaris buildbots automatically uploading binaries.

The wiki currently has this text:
----------------8<-------------------------------
Several darcs builtbots are configured in a way that they upload the latest
greatest darcs binary produced by the last successful build to the publicly
available host on the Internet. Have a look here for the list of snapshots:
https://zooko.com/darcsbuildbot/uploads/

Note: since Zooko does not have CA signed certificate you will need to accept
the security exception in your browser. How to do it depends on your browser
software. 
-------------8<---------------------------

What may be nicer is to have a link to each binary separately with a description
of the corresponding build slave.  We don't necessarily have to automate it,
just find a good way to cut and paste the information from somewhere.

Another thing that would help is to find a way to deal with the problem that
anybody visiting zooko.com gets "zooko.com uses an invalid security
certificate.".  First impressions count and for most people that message just
means "run away!"

One solution I will not be able to support right now is: finding a wiki which
will allow for software uploads (no time, nor anybody to delegate to with time,
plus I don't want to launch us into a wiki bikeshed ond besides, we already want
to try gitit+darcs}).

The bad news is that the integration of nightlies into buildbot is broken
(largely by our abandoning autoconf/make in favour af Cabal).

Petr has convinced me that the intersection between users who want bleeding edge
builds and users who binaries is too small for this to be a good investment of
our time.

http://irclog.perlgeek.de/darcs/2009-08-04#i_1364855

Sorry! More manpower needed!

Petr had convinced me that nightly binaries was too much a fringe case to be
worth the effort.

On the other hand, Jason just brought up the suggestion of automatically
building *tagged* builds of darcs, which would be more more useful, in my opinion.