Use substring completion for Info menus and index

* lisp/info.el (Info-complete-menu-item): Add `category' metadata.
(Info-menu): Simplify now that we use the `default' arg of completing-read.
* lisp/minibuffer.el (completion-category-defaults): Use substring
completion for `info-menu`.

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 76c9dbc3315..72818278781 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -386,6 +386,10 @@ end of the word).
 
 * Changes in Specialized Modes and Packages in Emacs 26.1
 
+*** Info menu and index completion uses substring completion by default.
+This can be customized via the `info-menu` category in
+completion-category-override.
+
 +++
 *** The ancestor buffer is shown by default in 3way merges.
 A new option ediff-show-ancestor and a new toggle