Exception during merge --lca

Hi,

Forwarding from Debian.

I get the following exception when trying to merge a feature branch
into an integration branch:
,----
| roland@mirexpress ~/debian/f-spot+superpatch $ bzr merge --lca /home/roland/debian/bzr-repo/f-spot/patches/bz-329174
| Warning: criss-cross merge encountered. See bzr help criss-cross.
| bzr: ERROR: exceptions.IndexError: list index out of range
|
| Traceback (most recent call last):
| File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 806, in run_bzr_catch_errors
| return run_bzr(argv)
| File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 762, in run_bzr
| ret = run(*run_argv)
| File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 492, in run_argv_aliases
| return self.run(**all_cmd_args)
| File "/usr/lib/python2.4/site-packages/bzrlib/builtins.py", line 2862, in run
| conflict_count = merger.do_merge()
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 410, in do_merge
| change_reporter=self.change_reporter,
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 1025, in __init__
| change_reporter=change_reporter)
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 511, in __init__
| file_status = self.merge_contents(file_id)
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 808, in merge_contents
| self.text_merge(file_id, trans_id)
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 1053, in text_merge
| lines, conflicts = self._merged_lines(file_id)
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 1089, in _merged_lines
| return textmerge.merge_lines(self.reprocess)
| File "/usr/lib/python2.4/site-packages/bzrlib/textmerge.py", line 86, in merge_lines
| for group in self.merge_struct(reprocess):
| File "/usr/lib/python2.4/site-packages/bzrlib/textmerge.py", line 72, in iter_useful
| for group in struct_iter:
| File "/usr/lib/python2.4/site-packages/bzrlib/versionedfile.py", line 652, in _merge_struct
| for state, line in self.plan:
| File "/usr/lib/python2.4/site-packages/bzrlib/merge.py", line 1264, in _iter_plan
| yield 'conflicted-b', self.lines_b[a_index]
| IndexError: list index out of range
|
| bzr 1.1.0.candidate.1 on python 2.4.4.final.0 (linux2)
| arguments: ['/usr/bin/bzr', 'merge', '--lca', '/home/roland/debian/bzr-repo/f-spot/patches/bz-329174']
| encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'fr_FR.UTF-8'
| plugins:
| bisect /home/roland/.bazaar/plugins/bisect [1.1.0pre0]
| bzrtools /usr/lib/python2.4/site-packages/bzrlib/plugins/bzrtools [1.1.0]
| email /usr/lib/python2.4/site-packages/bzrlib/plugins/email [unknown]
| gtk /usr/lib/python2.4/site-packages/bzrlib/plugins/gtk [0.93.0]
| launchpad /usr/lib/python2.4/site-packages/bzrlib/plugins/launchpad [unknown]
| multiparent /usr/lib/python2.4/site-packages/bzrlib/plugins/multiparent.pyc [unknown]
| rebase /usr/lib/python2.4/site-packages/bzrlib/plugins/rebase [0.3.0]
| svn /usr/lib/python2.4/site-packages/bzrlib/plugins/svn [0.4.7]
| *** Bazaar has encountered an internal error.
| Please report a bug at https://bugs.launchpad.net/bzr/+filebug
| including this traceback, and a description of what you
| were doing when the error occurred.
| roland@mirexpress ~/debian/f-spot+superpatch $
`----

  This seems to be reproducible in a clean chroot even with bzr 1.2
and no plugins. The branches are public and move as time passes, but
I made a snapshot, so the following steps should allow reproducing the
problem:

,----
| bzr branch http://bzr.debian.org/~lolando/tmp/bzrbug-20080228/superpatch/
| cd superpatch
| bzr merge --lca http://bzr.debian.org/~lolando/tmp/bzrbug-20080228/bz-329174/
`----

  Merging with --diff3 or --weave doesn't exhibit that behaviour.

Roland.