Doesn't know about non-command help topics

 status confirmed
 importance critical

If you want to fix it, I suggest querying for topics and if the command
being looked up is a topic just bail out with None early. This is
happening because the 'command' help topic just asks for the command.
Doing what I suggest here will mean that 'bzr hidden-commands' will
return no such command and not suggest one - which I think is fine.

-Rob

Thinking about this more, some other options that might be better.
 - stop guessing when doing help
 - add a similar mechanism to help for 'nothing found' and use that to do the same thing for help topics, when nothing is found

it became unbearable to not have bash auto completion of bzr commands, so I did a quick and dirty fix.
see linked branch.

A bare 'bzr help' gives:

bzr help
bzr: ERROR: exceptions.SystemError: NULL result without error in PyObject_Call

Traceback (most recent call last):
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 843, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 1044, in run_bzr
    ret = run(*run_argv)
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 655, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 1059, in ignore_pipe
    result = func(*args, **kwargs)
  File "/home/vila/src/bzr/trunk/bzrlib/builtins.py", line 4158, in run
    bzrlib.help.help(topic)
  File "/home/vila/src/bzr/trunk/bzrlib/help.py", line 46, in help
    topics = indices.search(topic)
  File "/home/vila/src/bzr/trunk/bzrlib/help.py", line 156, in search
    result.extend([(index, _topic) for _topic in index.get_topics(topic)])
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 1172, in get_topics
    cmd = _get_cmd_object(topic)
  File "/home/vila/src/bzr/trunk/bzrlib/commands.py", line 238, in _get_cmd_object
    cmd = hook(cmd_name)
  File "/home/vila/.bazaar/plugins/guess/__init__.py", line 38, in guess_command
    matcher = patiencediff.PatienceSequenceMatcher(None, cmd_name, name)
SystemError: NULL result without error in PyObject_Call

bzr 2.1.0dev4 on python 2.6.4 (Linux-2.6.31-15-generic-x86_64-with-Ubuntu-9.10-karmic)
arguments: ['/home/vila/bin/bzr', 'help']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'
plugins:
  bookmarks /home/vila/.bazaar/plugins/bookmarks [unknown]
  builddeb /home/vila/.bazaar/plugins/builddeb [2.1.1dev]
  builder /home/vila/.bazaar/plugins/builder [unknown]
  bzrtools /home/vila/.bazaar/plugins/bzrtools [2.1.0b1]
  diffstat /home/vila/.bazaar/plugins/diffstat [0.2.0]
  email /home/vila/.bazaar/plugins/email [unknown]
  explorer /home/vila/.bazaar/plugins/explorer [0.10.0dev]
  fix277537 /home/vila/.bazaar/plugins/fix277537 [unknown]
  gtk /home/vila/.bazaar/plugins/gtk [0.98.0dev1]
  guess /home/vila/.bazaar/plugins/guess [unknown]
  launchpad /home/vila/src/bzr/trunk/bzrlib/plugins/launchpad [2.1.0dev4]
  local_test_server /home/vila/.bazaar/plugins/local_test_server [unknown]
  loom /home/vila/.bazaar/plugins/loom [1.4.0dev]
  netrc_credential_store /home/vila/src/bzr/trunk/bzrlib/plugins/netrc_credential_store [2.1.0dev4]
  qbzr /home/vila/.bazaar/plugins/qbzr [0.17.0dev]
  stats /home/vila/.bazaar/plugins/stats [unknown]
  upload /home/vila/.bazaar/plugins/upload [1.0.0dev]

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.

I fixed it, went to report the bug, saw he fixed it in the same way.

So, bzr.dev now has a permanent fix, we should, after 2.2.0 is released, remove the stack inspection code from bzr-guess.