patch 9.1.1396: 'errorformat' is a global option

Problem:  The 'grepformat' option is global option, but it would be
          useful to have it buffer-local, similar to 'errorformat' and
          other quickfix related options (Dani Dickstein)
Solution: Add the necessary code to support global-local 'grepformat',
          allowing different buffers to parse different grep output
          formats (glepnir)

fixes: #17316
closes: #17315

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 274d56e..e74c5e8 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 May 14
+*options.txt*	For Vim version 9.1.  Last change: 2025 May 16
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -4062,7 +4062,7 @@
 
 						*'grepformat'* *'gfm'*
 'grepformat' 'gfm'	string	(default "%f:%l:%m,%f:%l%m,%f  %l%m")
-			global
+			global or local to buffer |global-local|
 	Format to recognize for the ":grep" command output.
 	This is a scanf-like string that uses the same format as the
 	'errorformat' option: see |errorformat|.