[BUG?] update after merge to empty branch misbehaving

[Alexander Belchenko]

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OK, I finally found sequence of commands that cause traceback
with update command.

bzr init a
bzr branch a b
echo foo > a/bar
bzr add a/bar
bzr ci a -m 1
cd b
bzr merge
bzr update

Python 2.4 and 2.5 and 2.5.1 with bzr.dev on win32
don't print traceback, but report about error:

E:\temp\1\b>bzr update
- -D  bar
All changes applied successfully.
bzr: ERROR: Reserved revision-id {null:}

But problem exists in 0.90 with any version of Python:

E:\temp\1\b>python E:/Python24/Scripts/bzr update
- -D  bar
All changes applied successfully.
Updated to revision 0.
bzr: ERROR: exceptions.TypeError: sequence item 1: expected string, NoneType found

Traceback (most recent call last):
  File "E:\Python24\Lib\site-packages\bzrlib\commands.py", line 817, in run_bzr_catch_errors
    return run_bzr(argv)
  File "E:\Python24\Lib\site-packages\bzrlib\commands.py", line 779, in run_bzr
    ret = run(*run_argv)
  File "E:\Python24\Lib\site-packages\bzrlib\commands.py", line 477, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "E:\Python24\Lib\site-packages\bzrlib\builtins.py", line 1050, in run
    tree.unlock()
  File "E:\Python24\Lib\site-packages\bzrlib\workingtree_4.py", line 1125, in unlock
    self.flush()
  File "E:\Python24\Lib\site-packages\bzrlib\workingtree_4.py", line 312, in flush
    self.current_dirstate().save()
  File "E:\Python24\Lib\site-packages\bzrlib\dirstate.py", line 1639, in save
    self._state_file.writelines(self.get_lines())
  File "E:\Python24\Lib\site-packages\bzrlib\dirstate.py", line 1224, in get_lines
    lines.append(self._get_parents_line(self.get_parent_ids()))
  File "E:\Python24\Lib\site-packages\bzrlib\dirstate.py", line 1236, in _get_parents_line
    return '\0'.join([str(len(parent_ids))] + parent_ids)
TypeError: sequence item 1: expected string, NoneType found

bzr 0.90.0 on python 2.4.4.final.0 (win32)
arguments: ['E:/Python24/Scripts/bzr', 'update']

** please send this report to bazaar at lists.ubuntu.com
E:\Python24\lib\site-packages\bzrlib\lockable_files.py:110: UserWarning: file group
LockableFiles(<bzrlib.transport.local.LocalT
ransport url=file:///E:/temp/1/b/.bzr/checkout/>) was not explicitly unlocked
  warn("file group %r was not explicitly unlocked" % self)


I think update command anyway is incorrect here,
because when branch has at least 1 committed revision
update don't change anything.

But as you can see from logs above, when there is no revisions,
update remove files added by merge.

Hm?

[µ]
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