refactor(terminal): move :terminal defaults to _defaults.lua

runtime/doc/news.txt

@@ -140,6 +140,8 @@ TERMINAL
 
 • The |terminal| now understands the OSC 52 escape sequence to write to the
   system clipboard (copy). Querying with OSC 52 (paste) is not supported.
+• |hl-StatusLineTerm| and |hl-StatusLineTermNC| define highlights for the
+  status line in |terminal| windows.
 
 TREESITTER
 

runtime/doc/syntax.txt

@@ -5111,7 +5111,7 @@ StatusLineNC	Status lines of not-current windows.
 StatusLineTerm	Status line of |terminal| window.
 							*hl-StatusLineTermNC*
 StatusLineTermNC
-		Status line of non-current |terminal| window.
+		Status line of non-current |terminal| windows.
 							*hl-TabLine*
 TabLine		Tab pages line, not active tab page label.
 							*hl-TabLineFill*

runtime/doc/vim_diff.txt

@@ -166,6 +166,14 @@ nvim_terminal:
   when 'background' is "light". While this may not reflect the actual
   foreground/background color, it permits 'background' to be retained for a
   nested Nvim instance running in the terminal emulator.
+- TermOpen: Sets default options for |terminal| buffers:
+    - 'nomodifiable'
+    - 'undolevels' set to -1
+    - 'textwidth' set to 0
+    - 'nowrap'
+    - 'nolist'
+    - 'winhighlight' uses |hl-StatusLineTerm| and |hl-StatusLineTermNC| in
+      place of |hl-StatusLine| and |hl-StatusLineNC|
 
 nvim_cmdwin:
 - CmdwinEnter: Limits syntax sync to maxlines=1 in the |cmdwin|.
@@ -538,6 +546,8 @@ Highlight groups:
 - Highlight groups names are allowed to contain `@` characters.
   - It is an error to define a highlight group with a name that doesn't match
     the regexp `[a-zA-Z0-9_.@-]*` (see |group-name|).
+- |hl-StatusLineTerm| |hl-StatusLineTermNC| are implemented as 'winhighlight'
+  window-local highlights which are set by the default |TermOpen| handler.
 
 Macro (|recording|) behavior:
 - Replay of a macro recorded during :lmap produces the same actions as when it
@@ -665,17 +675,6 @@ Events:
 - *SafeStateAgain*
 - *SigUSR1* Use |Signal| to detect `SIGUSR1` signal instead.
 
-Highlight groups:
-- *hl-StatusLineTerm* *hl-StatusLineTermNC* are unnecessary because Nvim
-  supports 'winhighlight' window-local highlights. For example, to mimic Vim's
-  StatusLineTerm:  >vim
-      hi StatusLineTerm ctermfg=black ctermbg=green
-      hi StatusLineTermNC ctermfg=green
-      autocmd TermOpen,WinEnter * if &buftype=='terminal'
-        \|setlocal winhighlight=StatusLine:StatusLineTerm,StatusLineNC:StatusLineTermNC
-        \|else|setlocal winhighlight=|endif
-<
-
 Options:
 - *'aleph'* *'al'*
 - antialias

runtime/lua/vim/_defaults.lua

@@ -282,6 +282,26 @@ do
     end,
   })
 
+  vim.api.nvim_create_autocmd('TermOpen', {
+    group = nvim_terminal_augroup,
+    desc = 'Default settings for :terminal buffers',
+    callback = function()
+      vim.bo.modifiable = false
+      vim.bo.undolevels = -1
+      vim.bo.scrollback = vim.o.scrollback < 0 and 10000 or math.max(1, vim.o.scrollback)
+      vim.bo.textwidth = 0
+      vim.wo.wrap = false
+      vim.wo.list = false
+
+      -- This is gross. Proper list options support when?
+      local winhl = vim.o.winhighlight
+      if winhl ~= '' then
+        winhl = winhl .. ','
+      end
+      vim.wo.winhighlight = winhl .. 'StatusLine:StatusLineTerm,StatusLineNC:StatusLineTermNC'
+    end,
+  })
+
   vim.api.nvim_create_autocmd('CmdwinEnter', {
     pattern = '[:>]',
     desc = 'Limit syntax sync to maxlines=1 in the command window',