How to communicate with upstream sources intelligently

[Jari Aalto+usenet]

I need comments how to best arrange conversation with upstream in
following situation. Both parties use different version control (me:
bzr, upstream svn).

INITIAL SITUATION

    upstream        import to local TRUNK (bzr init; bzr ci)
    v1.0            => imported copy from tar.gz

CURRENT WORK FLOW

    The packages could use some improvements, isolate changes, so make
    branch for each:

    local TRUNK        => branch to change-1.0-A
                       => branch to change-1.0-B
                       => branch to change-1.0-C

    Write code, test, and submit individual patches to
    upstream from the branches (bzr diff):

        patch-1.0-A
        patch-1.0-B
        patch-1.0-C

    Upstream accepts A, and C. Did not yet respond to B. In the mean
    while time passes and upstream releases v1.1, which needs to be
    imported to TRUNK to make it current.

    upstream        local TRUNK (bzr ci)
    v1.1            => untar *.tar.gz and "ci" this as "1.1"

    Now, the branches A and C are no longer needed, but
    what should be done to B? Suppose that the source has
    changed significantly, so what is the easiest way
    to merge

        1.1 + changes in branch-1.0-B 

    to make it branch-1.1-B and submit that to upstream?

I'm sure I'm not using brz to its fullest potential yet, so please
welcome improvements and ideas that might work better.

Jari