Normally in Mercurial the main branch is called "default." In the pip
repository, because of how it was imported from Subversion, the main branch
has historically been "trunk" instead.  This has occasionally caused
difficulty, as some Mercurial-related tools assume they can find a "default"
branch.

The trunk branch has now been closed (in changeset e3e765036db8), and
replaced by a default branch (beginning in changeset 8c23d896d458). To
create these two commits, I ran the following commands:

$ hg commit -m 'close "trunk" branch' --close-branch
$ hg branch default
$ hg commit -m 'start default branch'

If we now merge in changes from people who have committed their new
changesets on the "trunk" branch, my testing indicates that will reopen the
trunk branch.  We could avoid this by asking them to re-fork the repo and
re-commit their changes on the new default branch.  Otherwise, we need to
re-close the trunk branch after pulling their commit. We would do that like
this:

$ hg pull http://bitbucket.org/somebody/pip
$ hg up trunk  # update to their latest commit, on "trunk"
$ hg commit -m 'close trunk branch, again'
$ hg up default # update back to mainline
$ hg merge trunk 
$ hg commit -m 'merged changes from somebody'

(Yes, it seems like it ought to be possible to merge a branch and close it
in one step, but AFAICT it is not. You have to first close it, then merge
it.)
