vim-patch:8.2.4336: using :filter for :scriptnames does not work

Problem:    Using :filter for :scriptnames does not work. (Ben Jackson)
Solution:   Call message_filtered(). (closes vim/vim#9720)
769f5895eb

Cherry-pick a modeline from Vim patch 8.2.1432.

src/nvim/ex_cmds2.c

@@ -12,6 +12,7 @@
 #include <string.h>
 
 #include "nvim/ascii.h"
+#include "nvim/globals.h"
 #include "nvim/vim.h"
 #ifdef HAVE_LOCALE_H
 # include <locale.h>
@@ -2190,9 +2191,11 @@ void ex_scriptnames(exarg_T *eap)
     if (SCRIPT_ITEM(i).sn_name != NULL) {
       home_replace(NULL, SCRIPT_ITEM(i).sn_name, NameBuff, MAXPATHL, true);
       vim_snprintf((char *)IObuff, IOSIZE, "%3d: %s", i, NameBuff);
-      msg_putchar('\n');
-      msg_outtrans(IObuff);
-      line_breakcheck();
+      if (!message_filtered(IObuff)) {
+        msg_putchar('\n');
+        msg_outtrans(IObuff);
+        line_breakcheck();
+      }
     }
   }
 }

src/nvim/testdir/test_filter_cmd.vim

@@ -172,3 +172,11 @@ func Test_filter_display()
 
   bwipe!
 endfunc
+
+func Test_filter_scriptnames()
+  let lines = split(execute('filter /test_filter_cmd/ scriptnames'), "\n")
+  call assert_equal(1, len(lines))
+  call assert_match('filter_cmd', lines[0])
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab