[Python-Dev] crosses branches?

[skip at pobox.com]

I came across a new message I neither understood before or after searching
for it on Google (and thus the documentation):

    % hg pull -u
    pulling from /Users/skip/src/hgpython/2.6
    searching for changes
    adding changesets
    adding manifests
    adding file changes
    added 242 changesets with 766 changes to 263 files
    abort: crosses branches (use 'hg merge' or use 'hg update -c')

What does "crosses branches" mean?  From the couple instances I saw in the
docs I found I couldn't tell.

This was in my 2.5 repository, which I recall Guido saying he updated
recently (copyright file or something?).

I should point out that I have a local commit which I don't want to push.
That fixes the build problem with the unexpanded $HeadURL$ svn keyword:

    changeset:   68309:c3caaf979b9e
    branch:      2.5
    parent:      68263:7790ad8332ba
    user:        Skip Montanaro <skip at pobox.com>
    date:        Sun Mar 06 21:31:25 2011 -0600
    summary:     manually expand the defunct HeadURL subversion keyword

Skip