refactor: fix clang/PVS warnings (#23731)

src/nvim/ex_docmd.c

@@ -48,7 +48,6 @@
 #include "nvim/highlight_group.h"
 #include "nvim/input.h"
 #include "nvim/keycodes.h"
-#include "nvim/lua/secure.h"
 #include "nvim/macros.h"
 #include "nvim/main.h"
 #include "nvim/mark.h"

src/nvim/fileio.c

@@ -3481,8 +3481,7 @@ void vim_deltempdir(void)
 char *vim_gettempdir(void)
 {
   static int notfound = 0;
-  bool exists = false;
-  if (vim_tempdir == NULL || !(exists = os_isdir(vim_tempdir))) {
+  if (vim_tempdir == NULL || !os_isdir(vim_tempdir)) {
     if (vim_tempdir != NULL) {
       notfound++;
       if (notfound == 1) {

src/nvim/generators/gen_ex_cmds.lua

@@ -55,6 +55,7 @@ defsfile:write(string.format([[
 #include "nvim/help.h"
 #include "nvim/indent.h"
 #include "nvim/lua/executor.h"
+#include "nvim/lua/secure.h"
 #include "nvim/mapping.h"
 #include "nvim/mark.h"
 #include "nvim/match.h"

src/nvim/lua/executor.c

@@ -341,7 +341,7 @@ static int nlua_init_argv(lua_State *const L, char **argv, int argc, int lua_arg
     lua_pushstring(L, argv[lua_arg0 - 1]);
     lua_rawseti(L, -2, 0);  // _G.arg[0] = "foo.lua"
 
-    for (; lua_arg0 >= 0 && i + lua_arg0 < argc; i++) {
+    for (; i + lua_arg0 < argc; i++) {
       lua_pushstring(L, argv[i + lua_arg0]);
       lua_rawseti(L, -2, i + 1);  // _G.arg[i+1] = "--foo"
     }

src/nvim/lua/secure.c

@@ -1,3 +1,6 @@
+// This is an open source non-commercial project. Dear PVS-Studio, please check
+// it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+
 #include <lauxlib.h>
 #include <lua.h>
 #include <lualib.h>