"darcs record; darcs send; darcs unrecord --last=1" fails in (partial) ghc head repo

[Claus Reinke]

context:

    - i'm working on patches for ghc head
    - to send the patches for review, i'm supposed to use 'darcs send',
        which means i need to 'darcs record' them
    - the patches evolve in discussion until they get accepted,
        so i can't keep the interim versions of the patches recorded

the issue:

i thought that using

    darcs record; darcs send; darcs unrecord --last=1

would do what i need: being able to send a patch without keeping
it recorded in my local repo. but it fails:

    $ darcs unrecord --last=1
    
    Mon Sep 17 11:41:51 GMT Daylight Time 2007  claus.reinke at talk21.com
      * ghci :browse! :{:} :set :show languages/packages
    ..
    Shall I unrecord this patch? (1/1)  [ynWvpxqadjk], or ? for help:
    realdarcs.exe: failed to read patch in get_extra:
    Fri Dec 15 21:44:30 GMT Standard Time 2006  Ian Lynagh <igloo at earth.li>
      * Free more things that we allocate
    Perhaps this is a 'partial' repository?

    $ darcs -v
    1.0.9 (release)
    
    $ which darcs
    /cygdrive/c/darcs/darcsdir-cygwin/darcs

i have no idea whyever darcs would need to look beyond the last
patch if that is all i want to unrecord, so why is partial/complete
repo even an issue here? looks like a bug to me.

and is there a workaround that could help me avoid throwing away 
my repo and waiting a few days while pulling the huge complete repo 
over my slow connection?

is darcs really not useable with partial repos? that would be a pain.
i know that several ghc developers have already given up on partial
repos (there's even a good old-fashioned tarball to start from...).

if partial repos are unusable at the moment, what is the target date 
for fixing this issue?

thanks,
claus