Update runtime files
diff --git a/runtime/doc/usr_40.txt b/runtime/doc/usr_40.txt
index 9ed777f..af5c5d0 100644
--- a/runtime/doc/usr_40.txt
+++ b/runtime/doc/usr_40.txt
@@ -1,4 +1,4 @@
-*usr_40.txt* For Vim version 8.2. Last change: 2022 Jan 03
+*usr_40.txt* For Vim version 8.2. Last change: 2022 Jun 20
VIM USER MANUAL - by Bram Moolenaar
@@ -463,6 +463,17 @@
The optional [++nested] flag allows for nesting of autocommands (see below),
and finally, {command} is the command to be executed.
+When adding an autocommand the already existing ones remain. To avoid adding
+the autocommand several time you should use this form: >
+
+ :augroup updateDate
+ : autocmd!
+ : autocmd BufWritePre * call DateInsert()
+ :augroup END
+
+This will delete any previously defined autocommand with `:autocmd!` before
+defining the new one. Groups are explained later.
+
EVENTS