'inccommand': rework

- Eliminate/isolate static/global variables
- Remove special-case parameter from buflist_new()
- Remove special-case ECMD_RESERVED_BUFNR
- To determine when u_undo_and_forget() should be done, check
  b_changedtick instead of a heuristic.
- use mb_string2cells() instead of strlen() to measure the :sub patterns
- call ml_close() before buf_clear_file(). Avoids leaks caught by ASan.

Original patch by:
  Robin Elrharbi-Fleury (Robinhola)
  Audrey Rayé (Adrey06)
  Philémon Hullot (DesbyP)
  Aymeric Collange (aym7)
  Clément Guyomard (Clement0)

runtime/doc/intro.txt

@@ -450,7 +450,7 @@ notation	meaning		    equivalent	decimal value(s)	~
 <k0> - <k9>	keypad 0 to 9			*keypad-0* *keypad-9*
 <S-...>		shift-key			*shift* *<S-*
 <C-...>		control-key			*control* *ctrl* *<C-*
-<M-...>		alt-key or meta-key		*meta* *alt* *<M-*
+<M-...>		alt-key or meta-key		*META* *meta* *alt* *<M-*
 <A-...>		same as <M-...>			*<A-*
 <D-...>		command-key or "super" key	*<D-*
 <t_xx>		key with "xx" entry in termcap

runtime/doc/options.txt

@@ -3526,6 +3526,14 @@ A jump table for the options with a short description can be found at |Q_op|.
 	CTRL-R CTRL-W can be used to add the word at the end of the current
 	match, excluding the characters that were already typed.
 
+						*'incsubstitute'* *'ics'*
+'incsubstitute' 'ics'	string	(default "")
+			global
+			
+	If "split" or "nosplit" then |:substitute| updates the buffer
+	as-you-type.  If "split", also show partial off-screen results in
+	a window.  Replacement text is hightlighted with |hl-IncSubstitute|.
+
 						*'indentexpr'* *'inde'*
 'indentexpr' 'inde'	string	(default "")
 			local to buffer
@@ -3992,16 +4000,6 @@ A jump table for the options with a short description can be found at |Q_op|.
 	"precedes".  "SpecialKey" for "nbsp", "space", "tab" and "trail".
 	|hl-NonText| |hl-SpecialKey|
 
-						*'incsubstitute'* *'ics'*
-'incsubstitute' 'ics'	string	(default "")
-			global
-			
-	If set to "split" or "nosplit", substitutions (|:s|) are updated live
-	while the user types the command.  If set to "split", a split window
-	is open which displays the lines where the search matches. The
-	replacement text in the split is hightlighted using
-	|hl-IncSubstitute|. Note: Only '/' is supported as a delimiter.
-
 			*'lpl'* *'nolpl'* *'loadplugins'* *'noloadplugins'*
 'loadplugins' 'lpl'	boolean	(default on)
 			global

runtime/doc/syntax.txt

@@ -4852,11 +4852,11 @@ SignColumn	column where |signs| are displayed
 							*hl-IncSearch*
 IncSearch	'incsearch' highlighting; also used for the text replaced with
 		":s///c"
+							*hl-IncSubstitute*
+IncSubstitute	'incsubstitute' replacement text
 							*hl-LineNr*
 LineNr		Line number for ":number" and ":#" commands, and when 'number'
 		or 'relativenumber' option is set.
-							*hl-IncSubstitute*
-IncSubstitute	The replacement text when using the |incsubstitute| functionality
 							*hl-CursorLineNr*
 CursorLineNr	Like LineNr when 'cursorline' or 'relativenumber' is set for
 		the cursor line.

runtime/doc/vim_diff.txt

@@ -64,7 +64,7 @@ these differences.
 3. New Features						       *nvim-features*
 
 
-MAJOR FEATURES ~
+MAJOR COMPONENTS ~
 
 Embedded terminal emulator	|terminal-emulator|
 RPC API				|RPC|
@@ -85,25 +85,29 @@ avoids features that cannot be provided on all platforms--instead that is
 delegated to external plugins/extensions.
 
 
-OTHER FEATURES ~
+ARCHITECTURE ~
+
+External plugins run in separate processes. |remote-plugin| This improves
+stability and allows those plugins to perform tasks without blocking the
+editor. Even "legacy" Python and Ruby plugins which use the old Vim interfaces
+(|if_py| and |if_ruby|) run out-of-process.
+
+
+FEATURES ~
 
 |bracketed-paste-mode| is built-in and enabled by default.
 
-Meta (alt) chords are recognized (even in the terminal).
-  <M-1>, <M-2>, ...
-  <M-BS>, <M-Del>, <M-Ins>, ...
-  <M-/>, <M-\>, ...
-  <M-Space>, <M-Enter>, <M-=>, <M-->, <M-?>, <M-$>, ...
-
-  Note: Meta chords are case-sensitive (<M-a> is distinguished from <M-A>).
+|META| (ALT) chords are recognized, even in the terminal. Any |<M-| mapping
+will work. Some examples: <M-1>, <M-2>, <M-BS>, <M-Del>, <M-Ins>, <M-/>,
+<M-\>, <M-Space>, <M-Enter>, <M-=>, <M-->, <M-?>, <M-$>, ...
+META chords are case-sensitive: <M-a> and <M-A> are two different keycodes.
 
 Some `CTRL-SHIFT-...` key chords are distinguished from `CTRL-...` variants
 (even in the terminal). Specifically, the following are known to work:
-  <C-Tab>, <C-S-Tab>
-  <C-BS>, <C-S-BS>
-  <C-Enter>, <C-S-Enter>
+  <C-Tab>, <C-S-Tab>, <C-BS>, <C-S-BS>, <C-Enter>, <C-S-Enter>
 
 Options:
+  'incsubstitute' shows results while typing a |:substitute| command
   'statusline' supports unlimited alignment sections
   'tabline' %@Func@foo%X can call any function on mouse-click
 
@@ -125,14 +129,14 @@ Functions:
 Events:
   |TabNew|
   |TabNewEntered|
-  |TabClosed|
-  |TermOpen|
   |TermClose|
+  |TermOpen|
   |TextYankPost|
 
 Highlight groups:
-  |hl-EndOfBuffer|
+  |hl-Substitute|
   |hl-QuickFixLine|
+  |hl-Substitute|
   |hl-TermCursor|
   |hl-TermCursorNC|
 
@@ -298,6 +302,7 @@ Other commands:
   :mode (no longer accepts an argument)
   :open
   :shell
+  :smile
   :tearoff
 
 Other compile-time features: