vim-patch:9.1.0864: message history is fixed to 200 (#31215)

Problem:  message history is fixed to 200
Solution: Add the 'msghistory' option, increase the default
          value to 500 (Shougo Matsushita)

closes: vim/vim#16048

4bd9b2b246

Co-authored-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Co-authored-by: Milly <milly.ca@gmail.com>

src/nvim/options.lua

@@ -3962,7 +3962,8 @@ return {
       desc = [=[
         A history of ":" commands, and a history of previous search patterns
         is remembered.  This option decides how many entries may be stored in
-        each of these histories (see |cmdline-editing|).
+        each of these histories (see |cmdline-editing| and 'msghistory' for
+        the number of messages to remember).
         The maximum value is 10000.
       ]=],
       full_name = 'history',
@@ -5757,6 +5758,19 @@ return {
       type = 'number',
       varname = 'p_mouset',
     },
+    {
+      abbreviation = 'mhi',
+      defaults = { if_true = 500 },
+      desc = [=[
+        Determines how many entries are remembered in the |:messages| history.
+        The maximum value is 10000.
+      ]=],
+      full_name = 'msghistory',
+      scope = { 'global' },
+      short_desc = N_('how many messages are remembered'),
+      type = 'number',
+      varname = 'p_mhi',
+    },
     {
       abbreviation = 'nf',
       cb = 'did_set_nrformats',