fix(lua): not using global value in vim.opt_global (#25196)

runtime/lua/vim/_options.lua

@@ -727,7 +727,10 @@ local function create_option_accessor(scope)
 
   return setmetatable({}, {
     __index = function(_, k)
-      return make_option(k, api.nvim_get_option_value(k, {}))
+      -- vim.opt_global must get global value only
+      -- vim.opt_local may fall back to global value like vim.opt
+      local opts = { scope = scope == 'global' and 'global' or nil }
+      return make_option(k, api.nvim_get_option_value(k, opts))
     end,
 
     __newindex = function(_, k, v)

test/functional/lua/vim_spec.lua

@@ -2257,8 +2257,8 @@ describe('lua stdlib', function()
     end)
   end) -- vim.opt
 
-  describe('opt_local', function()
+  describe('vim.opt_local', function()
-    it('should be able to append to an array list type option', function()
+    it('appends into global value when changing local option value', function()
       eq({ "foo,bar,baz,qux" }, exec_lua [[
         local result = {}
 
@@ -2273,6 +2273,19 @@ describe('lua stdlib', function()
     end)
   end)
 
+  describe('vim.opt_global', function()
+    it('gets current global option value', function()
+      eq({ "yes" }, exec_lua [[
+        local result = {}
+
+        vim.cmd "setglobal signcolumn=yes"
+        table.insert(result, vim.opt_global.signcolumn:get())
+
+        return result
+      ]])
+    end)
+  end)
+
   it('vim.cmd', function()
     exec_lua [[
     vim.cmd "autocmd BufNew * ++once lua BUF = vim.fn.expand('<abuf>')"