Bug? git-svn clone dies with "fatal: ambiguous argument '...': unknown revision or path not in the working tree."

I have been using git-svn happily for many months, updating git from git://git.kernel.org/pub/scm/git/git.git every once in a while. I just updated to c0eb604330e1288300d915f25868d1eed88d3038, and tried to clone the same svn repo that I've been using for a long time:

$ git svn clone http://svn/repos/cozi/kits --stdlayout

It chugged along happily for a while, but then died like this:

fatal: ambiguous argument '2d2df13977551168a54ffa9b706484242a58736a^..d038748d49a0de5802fe3c13f46d0e080d064290': unknown revision or path not in the working tree. Use '--' to separate paths from revisions rev-list 2d2df13977551168a54ffa9b706484242a58736a^..d038748d49a0de5802fe3c13f46d0e080d064290: command returned error: 128

"git show 2d2df13977551168a54ffa9b706484242a58736a" shows that the commit in question corresponds to a commit in svn that created an empty directory:

15:56:46 [COZIGROUP\erich@ubuntu64-erich kits] (master)$  git show -w
2d2df13977551168a54ffa9b706484242a58736a
commit 2d2df13977551168a54ffa9b706484242a58736a
Author: cozigroup\erich <cozigroup\erich@1248e456-dc32-5a46-b6cc-76877e1dc968>
Date:   Wed Jan 14 18:35:00 2009 +0000

    This branch will hold work I've done to refactor the vcs backend
stuff, and add support for Mercurial.

    git-svn-id: http://svn/repos/cozi/kits/branches/vcs-refactor@18735
1248e456-dc32-5a46-b6cc-76877e1dc968

15:41:01 [COZIGROUP\erich@ubuntu64-erich hmm]$ svn log --limit=1
-vr18735 http://svn/repos/cozi
------------------------------------------------------------------------
r18735 | cozigroup\erich | 2009-01-14 10:35:00 -0800 (Wed, 14 Jan
2009) | 2 lines
Changed paths:
   A /kits/branches/vcs-refactor

This branch will hold work I've done to refactor the vcs backend stuff, and add support for Mercurial.

If I recall correctly, that commit was a mistake: I'd forgotten that the proper way to create a branch in svn is to copy the trunk, and not to create an empty directory first.

Here I am creating that branch the proper way:

r18736 | cozigroup\erich | 2009-01-14 10:35:30 -0800 (Wed, 14 Jan
2009) | 2 lines
Changed paths:
   D /kits/branches/vcs-refactor

D'oh.  We branch by _copying_, not making empty directories :-|

------------------------------------------------------------------------
r18737 | cozigroup\erich | 2009-01-14 10:36:37 -0800 (Wed, 14 Jan
2009) | 2 lines
Changed paths:
   A /kits/branches/vcs-refactor (from /kits/trunk:18671)

Refactoring the version-control stuff, and adding Mercurial support.

------------------------------------------------------------------------

15:56:51 [COZIGROUP\erich@ubuntu64-erich kits] (master)$ git show -w
d038748d49a0de5802fe3c13f46d0e080d064290
commit d038748d49a0de5802fe3c13f46d0e080d064290
Merge: 5108824 a370f0b
Author: cozigroup\erich <cozigroup\erich@1248e456-dc32-5a46-b6cc-76877e1dc968>
Date:   Tue Jan 20 18:34:26 2009 +0000

    Merged from trunk.

    git-svn-id: http://svn/repos/cozi/kits/branches/vcs-refactor@18920
1248e456-dc32-5a46-b6cc-76877e1dc968

And here is (what might be) the first attempt to modify stuff in that directory:

15:52:52 [COZIGROUP\erich@ubuntu64-erich kits] (master)$ svn log
--limit=1 -vr18920 http://svn/repos/cozi
------------------------------------------------------------------------
r18920 | cozigroup\erich | 2009-01-20 10:34:26 -0800 (Tue, 20 Jan
2009) | 2 lines
Changed paths:
   M /kits/branches/vcs-refactor
   A /kits/branches/vcs-refactor/lib/CoziPlatform/cozi/resources.py
(from /kits/trunk/lib/CoziPlatform/cozi/resources.py:18919)
   M /kits/branches/vcs-refactor/lib/CoziSecurity/cozi/authorize.py
   M /kits/branches/vcs-refactor/lib/CoziSecurity/cozi/eguidtests.py
   M /kits/branches/vcs-refactor/lib/CoziVaultRESTServices/cozi/screen_saver_api.py
   M /kits/branches/vcs-refactor/lib/CoziVaultRESTServices/cozi/screen_saver_calendar_xml.tmpl
   M /kits/branches/vcs-refactor/lib/CoziVaultRESTServices/cozi/web_client.py

Merged from trunk.

Anyway -- I suspect that my svn repos layout is ... er ... unusual, and has hit some sorta edge case in git-svn. Is there some workaround I can use, or is this a bug?

Thanks