A branch that is downloaded from the drupal bzr server is just a copy of a branch. These sorts of branches, as we've already covered, are updated simply by running "bzr pull". This only works, though, if your branch is _just_ a copy. If you have committed to a branch, then a slightly different approach needs to be taken. A branch that has been committed to is a "diverged branch". These branches are different, but equally valid, from the branch they came from.

One merges changes between diverged branches with the "bzr merge" command. In your case, your branch will have diverged from the official drupal.dev branch. You can merge from drupal.dev in this way:

$ bzr merge

This will figue out what changes you are missing from official drupal.dev and apply them to your version of drupal. You're still not done, however. You should also review the changes in your branch and decide whether or not you want them. You can see what changed by running "bzr st" and how they changed by "bzr diff". Presumably you'll want to save the changes. You can do this the same way that you've always saved changes by

bzr commit -m 'merged from mainline'