patch 8.1.1542: an OptionSet autocommand does not get enough infov8.1.1542

Problem:    An OptionSet autocommand does not get enough info.
Solution:   Add v:option_command, v:option_oldlocal and v:option_oldglobal.
            (Latrice Wilgus, closes #4118)

3 files changed, 51 insertions, 11 deletions

diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index c82669514a..c922df18ac 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1,4 +1,4 @@
-*autocmd.txt*   For Vim version 8.1.  Last change: 2019 Jun 02
+*autocmd.txt*   For Vim version 8.1.  Last change: 2019 Jun 15
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -873,15 +873,33 @@ MenuPopup			Just before showing the popup menu (under the
 							*OptionSet*
 OptionSet			After setting an option.  The pattern is
 				matched against the long option name.
-				The |v:option_old| variable indicates the
-				old option value, |v:option_new| variable
-				indicates the newly set value, the
-				|v:option_type| variable indicates whether
-				it's global or local scoped and |<amatch>|
-				indicates what option has been set.
-
-				Is not triggered on startup and for the 'key'
-				option for obvious reasons.
+				|<amatch>| indicates what option has been set.
+
+				|v:option_type| indicates whether it's global
+				or local scoped
+				|v:option_command| indicates what type of
+				set/let command was used (follow the tag to
+				see the table).
+				|v:option_new| indicates the newly set value.
+				|v:option_oldlocal| hass the old local value.
+				|v:option_oldglobal| hass the old global
+				value
+				|v:option_old| indicates the old option value.
+
+				|v:option_oldlocal| is only set when |:set|
+				or |:setlocal| or a |modeline| was used to set
+				the option. Similarly |v:option_oldglobal| is
+				only set when |:set| or |:setglobal| was used.
+
+				Note that when setting a |global-local| string
+				option with |:set|, then |v:option_old| is the
+				old global value. However, for all other kinds
+				of options (local string options, global-local
+				number options, ...) it is the old local
+				value.
+
+				OptionSet is not triggered on startup and for
+				the 'key' option for obvious reasons.
 
 				Usage example: Check for the existence of the
 				directory in the 'backupdir' and 'undodir'
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index ca3f4ca065..83a89957f2 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1943,10 +1943,29 @@ v:option_new    New value of the option. Valid while executing an |OptionSet|
 		autocommand.
 						    *v:option_old*
 v:option_old    Old value of the option. Valid while executing an |OptionSet|
-		autocommand.
+		autocommand. Depending on the command used for setting and the
+		kind of option this is either the local old value or the
+		global old value.
+						    *v:option_oldlocal*
+v:option_oldlocal
+		Old local value of the option. Valid while executing an
+		|OptionSet| autocommand.
+						    *v:option_oldglobal*
+v:option_oldglobal
+		Old global value of the option. Valid while executing an
+		|OptionSet| autocommand.
 						    *v:option_type*
 v:option_type   Scope of the set command. Valid while executing an
 		|OptionSet| autocommand. Can be either "global" or "local"
+						    *v:option_command*
+v:option_command
+		Command used to set the option. Valid while executing an
+		|OptionSet| autocommand.
+			value		option was set via   ~
+			"setlocal"	|:setlocal| or ":let l:xxx"
+			"setglobal"	|:setglobal| or ":let g:xxx"
+			"set"		|:set| or |:let|
+			"modeline"	|modeline|
 					*v:operator* *operator-variable*
 v:operator	The last operator given in Normal mode.  This is a single
 		character except for commands starting with <g> or <z>,
diff --git a/runtime/doc/version8.txt b/runtime/doc/version8.txt
index 1dcef7efed..73db5f05b4 100644
--- a/runtime/doc/version8.txt
+++ b/runtime/doc/version8.txt
@@ -336,7 +336,10 @@ New Vim variables: ~
 |v:null|		an empty String, used for JSON
 |v:option_new|    	new value of the option, used by |OptionSet|
 |v:option_old|    	old value of the option, used by |OptionSet|
+|v:option_oldlocal|	old local value of the option, used by |OptionSet|
+|v:option_oldglobal|	old global value of the option, used by |OptionSet|
 |v:option_type|   	scope of the set command, used by |OptionSet|
+|v:option_command|	command used to set the option, used by |OptionSet|
 |v:progpath|		the command with which Vim was invoked
 |v:t_bool|		value of Boolean type
 |v:t_channel|		value of Channel type