Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>    When I try it, I don't get that.  Instead I just see "[Ambiguous dir name]"
>>    appended to the minibuffer for 2 seconds.
>
>> Then you must have a subdirectory of ~/ starting with `a'.
>
> No, that wasn't it.  It turns out the difference is that my shell is zsh.
> If I set SHELL to bash I can now reproduce your description.
>
> This happens to illustrate what I said earlier:
>> ... Of course, this part of the code is difficult to get right because it
>> uses an underlying shell to do the globbing ...
>
> I'll see if I can find a good fix for it,

  What about the following for PC-do-completion ?

  This patch fixes a minor issue with files containing spaces in their
  name, too. [1]

  However, I don't see what would be a « good fix » for the general
  completion function (not the PC one).