RE: dabbrev-completion doc string

[Drew Adams]

        The last sentence of the doc string should be removed, IMO:

          "With no prefix argument, it reuses an old completion list
           if there is a suitable one already."

    Thanks for pointing this out.  I will clarify it as follows to explain
    the user-level consequences.

    "With no prefix argument, it reuses an old completion list
    if there is a suitable one already.  This means that the
    list of completions may not be entirely up to date
    respect to the latest buffer contents."

The last line should start with "with".

Questions:

1. The start of the (complete) doc string suggests that nil has the effect
of limiting the set of buffers searched to the current buffer (at least that
was Luc's and my understanding, when reading it). That conflicts with saying
that nil means to reuse the existing list of completions (which might have
come from searching multiple buffer). This (at least perceived) conflict
needs to be cleared up in the doc string.

2. nil is the default value. Why do we _not_ recompute the list of
completions systematically? Is it to save time? If so, is that really
important here? Wouldn't it make more sense to use nil in the sense
suggested by the beginning of the doc string: search only the current
buffer?

Thanks,

  Drew