patch 8.2.4325: 'wildmenu' only shows few matches

Problem:    'wildmenu' only shows few matches.
Solution:   Add the "pum" option: use a popup menu to show the matches.
            (Yegappan Lakshmanan et al., closes #9707)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 732e5a7..ee2caa7 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8974,7 +8974,8 @@
 	mode.  On pressing 'wildchar' (usually <Tab>) to invoke completion,
 	the possible matches are shown just above the command line, with the
 	first match highlighted (overwriting the status line, if there is
-	one).  Keys that show the previous/next match, such as <Tab> or
+	one).  This is the behavior without "pum" in 'wildoptions.
+	Keys that show the previous/next match, such as <Tab> or
 	CTRL-P/CTRL-N, cause the highlight to move to the appropriate match.
 	When 'wildmode' is used, "wildmenu" mode is used where "full" is
 	specified.  "longest" and "list" do not start "wildmenu" mode.
@@ -8982,10 +8983,12 @@
 	If there are more matches than can fit in the line, a ">" is shown on
 	the right and/or a "<" is shown on the left.  The status line scrolls
 	as needed.
+	When 'wildoptions' contains "pum", then the completion matches are
+	shown in a popup menu.
 	The "wildmenu" mode is abandoned when a key is hit that is not used
 	for selecting a completion.
-	While the "wildmenu" is active the following keys have special
-	meanings:
+	While the "wildmenu" is active, not using the popup menu, the
+	following keys have special meanings:
 
 	<Left> <Right>	- select previous/next match (like CTRL-P/CTRL-N)
 	<Down>		- in filename/menu name completion: move into a
@@ -8995,6 +8998,21 @@
 	<Up>		- in filename/menu name completion: move up into
 			  parent directory or parent menu.
 
+	When using the popup menu for command line completion, the following
+	keys have special meanings:
+	<Down>		- select next match (like CTRL-N)
+	<Left>		- in filename/menu name completion: move up into
+			  parent directory or parent menu.
+	<Right>		- in filename/menu name completion: move into a
+			  subdirectory or submenu.
+	<Up>		- select previous match (like CTRL-P)
+	CTRL-E		- end completion, go back to what was there before
+			  selecting a match.
+	CTRL-N		- go to the next entry
+	CTRL-P		- go to the previous entry
+	CTRL-Y		- accept the currently selected match and stop
+			  completion.
+
 	This makes the menus accessible from the console |console-menus|.
 
 	If you prefer the <Left> and <Right> keys to move the cursor instead
@@ -9057,14 +9075,15 @@
 			global
 			{not available when compiled without the |+wildignore|
 			feature}
-	A list of words that change how command line completion is done.
-	Currently only one word is allowed:
+	A list of words that change how |cmdline-completion| is done.
+	The following values are supported:
+	  pum		Display the completion matches using the popupmenu
+			in the same style as the |ins-completion-menu|.
 	  tagfile	When using CTRL-D to list matching tags, the kind of
 			tag and the file of the tag is listed.	Only one match
 			is displayed per line.  Often used tag kinds are:
 				d	#define
 				f	function
-	Also see |cmdline-completion|.
 
 						*'winaltkeys'* *'wak'*
 'winaltkeys' 'wak'	string	(default "menu")