bug#2445: 23.0.90; file name completion GCs a lot

[Stefan Monnier <monnier@iro.umontreal.ca>]

>     Can you try the patch below to confirm it fixes your problem?
> The problem in my real cases is fixed given the sources as of
> yesterday.  It looks like you've identified fixes to other big
> slowdowns that arise in yet larger test cases.  I don't need them,
> but now that you've written them, you may as well install them
> unless they will cause trouble for someone.

Sorry about the email confusion: I wrote and sent the second email
first, but it got stuck on its machine and only got delivered much
later, at which point I had written the second email and installed the
fix already.

>     In the case of file completion, a simple (file-directory-p "xmail/")
>     would give us the necessary answer, but the code is generic and the
>     only/best way to get this information from a completion tables is to
>     call (try-completion "xmail/" table), which calls (file-name-completion
>     "" "xmail/").

> I have a feeling that (file-name-completion "" "xmail/") ought to
> first check (file-directory-p "xmail/") and return t if that does.

No: if all files in xmail/ start with "aba", then the above should
return "aba".


        Stefan