Confusing docs: doc/buildout.txt

The "Add a Package" part of doc/buildout.txt perplexes me. I ended up here because the "Upgrade a Package" section referred me to steps 4, 5 & 6.

Step 4 says, among other things:

    Look at the output. You need to see if it means that you have dependencies,
    some of which may be indirect dependencies. Here's an imaginary example
    output::

I don't know what I need to look out for. It also says:

    At this time, note that the output will include at least one, and possibly
    more, spurious "Picked:" listings. ipython, in particular, shows up
    repeatedly.

I don't think I saw that in my case.

Step 6 says:

6. Commit the changes (``cd download-cache``, ``bzr up``,
    ``bzr commit -m 'Add lazr.foom 1.1.2 and depdendencies to the download
    cache'``) to the shared download cache when you are sure it is what you
    want.

It doesn't say why I would want to do that (I'm given to understand it's not needed except for testing, which can be done in other ways) or why "bzr up" should make a difference. In my case, the only change was the creation of a tarball but there's no mention of "bzr add" or anything else that would need committing.