patch 9.1.0821: 'findexpr' completion doesn't set v:fname to cmdline argument

Problem:  'findexpr' completion doesn't set v:fname to cmdline argument.
Solution: Set v:fname to the cmdline argument as-is (zeertzjq).

closes: #15934

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 229ce13..e221fe3 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2024 Oct 22
+*options.txt*	For Vim version 9.1.  Last change: 2024 Oct 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -3567,6 +3567,10 @@
 	The expression is evaluated only once per |:find| command invocation.
 	The expression can process all the directories specified in 'path'.
 
+	The expression may be evaluated for command-line completion as well,
+	in which case the |v:cmdcomplete| variable will be set to |v:true|,
+	otherwise it will be set to |v:false|.
+
 	If a match is found, the expression should return a |List| containing
 	one or more file names.  If a match is not found, the expression
 	should return an empty List.
@@ -3586,7 +3590,8 @@
 >
 	    " Use glob()
 	    func FindExprGlob()
-		return glob(v:fname, v:false, v:true)
+		let pat = v:cmdcomplete ? $'{v:fname}*' : v:fname
+		return glob(pat, v:false, v:true)
 	    endfunc
 	    set findexpr=FindExprGlob()