bug#10771: TAB completion for info-display-manual

[Juri Linkov]

>> @@ -5138,7 +5138,7 @@ (defun info-display-manual (manual)
>>                     (apply-partially 'Info-read-node-name-2
>>                                      Info-directory-list
>>                                      (mapcar 'car Info-suffix-list))
>> -                   nil t))))
>> +                   nil nil))))
>>    (let ((blist (buffer-list))
>>      (manual-re (concat "\\(/\\|\\`\\)" manual "\\(\\.\\|\\'\\)"))
>>      (case-fold-search t)
>
> How is this better than the original command against which this bug
> was filed?

At least this is not worse than the original command that reads a manual name
without completion.  Completion is useful to read a manual name that is
not already visited.  So when you want to visit a new manual, you can use
completion, when a manual is already visited, you can type its name
and get it from the history with M-p.

BTW, there is another problem with selecting an Info buffer
by its Info file name: what if there are two Info buffers
visiting a manual with the same name.  Which one of them
should be preferred by this command?  Also which manual should be
preferred in completion when one manual is already visited
and another manual with the same name is available in Info-directory-list?