BetaBranches
http://package-import.ubuntu.com contains branches for (almost) all Ubuntu branches. They are read only mirrors of what is in the archive, and are kept up to date with any uploads to the archives.
You can grab the branches and use them to view the history of the package, or work on an update. However, as they are read-only you are unable to push your branch back. The Launchpad developers are working on a proper way to host source package branches, and when that is ready we will migrate there, and you will be able to push branches to launchpad.
There is also "loggerhead" a Bazaar web viewer running so that you can look at the branch without downloading it if you need.
There is documentation on how to retrieve these branches and how to use them to do some common things.
The branches are arranged similar to the "pool" on Ubuntu mirrors, grouped by the first letter of the source package name, with packages starting with "lib" being handled specially. For each source package there is then a branch for each Ubuntu release that that package was in. Here are a couple of examples of branches.
You can use these URLs with bzr to get a copy of the branch, or click on them to view it in loggerhead. Note that loggerhead currently inserts a "/loggerhead/" in to the URL when viewing it, so you will need to remove this to grab the branch with bzr if you take the URL from your URL bar. I am trying to find a way to remove this.
(Note that you should only need to look in the -upstream branches if they have some particular interest to you, they are not really required to be there as the other branches contain all the revisions anyway)
DistributedDevelopment/BetaBranches (last edited 2009-04-02 09:39:17 by i59F72099)