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

[Chong Yidong]

Eli Zaretskii <eliz@gnu.org> writes:

>> At least this is not worse than the original command that reads a
>> manual name without completion.
>
> I didn't say it was worse.  I asked how it was better.

How about adding existing Info buffers' manual names to the completion
table too, like the following?

=== modified file 'lisp/info.el'
*** lisp/info.el        2012-12-02 06:41:22 +0000
--- lisp/info.el        2012-12-03 06:55:15 +0000
***************
*** 5105,5113 ****
      (progn
        (info-initialize)
        (completing-read "Manual name: "
!                      (apply-partially 'Info-read-node-name-2
!                                       Info-directory-list
!                                       (mapcar 'car Info-suffix-list))
                       nil t))))
    (let ((blist (buffer-list))
        (manual-re (concat "\\(/\\|\\`\\)" manual "\\(\\.\\|\\'\\)"))
--- 5105,5111 ----
      (progn
        (info-initialize)
        (completing-read "Manual name: "
!                      (info--manual-names)
                       nil t))))
    (let ((blist (buffer-list))
        (manual-re (concat "\\(/\\|\\`\\)" manual "\\(\\.\\|\\'\\)"))
***************
*** 5126,5131 ****
--- 5124,5143 ----
        (info (Info-find-file manual)
            (generate-new-buffer-name "*info*")))))
  
+ (defun info--manual-names ()
+   (let (names)
+     (dolist (buffer (buffer-list))
+       (with-current-buffer buffer
+       (when (and (eq major-mode 'Info-mode)
+                  (stringp Info-current-file))
+         (push (file-name-sans-extension
+                (file-name-nondirectory Info-current-file))
+               names))))
+     (delete-dups (append names
+                        (apply-partially 'Info-read-node-name-2
+                                         Info-directory-list
+                                         (mapcar 'car Info-suffix-list))))))
+ 
  (provide 'info)
  
  ;;; info.el ends here