feat(ip): Add completion for monitor subcommand

Currently it stops after completing the first option, although you
should be able to choose multiple options.

Also include a test that is skipped if the monitor subcommand doesn't
exist.

Author: yedayak

completions/ip

@@ -357,7 +357,14 @@ _comp_cmd_ip()
                 all) ;;
                 *)
                     ((cword == subcword)) &&
-                        _comp_compgen -- -W 'help all'
+                        _comp_compgen_split -- "help all $(
+                            {
+                                "$1" -c=never monitor help || "$1" monitor help
+                            } 2>&1 | command sed -e \
+                                '/OBJECTS := /,/[^|]$/!d' -e \
+                                's/OBJECTS := *//' -e \
+                                's/|//g'
+                        )"
                     ;;
             esac
             ;;

test/t/test_ip.py

@@ -14,6 +14,15 @@ def test_2(self, completion):
     def test_r_r(self, completion):
         assert completion
 
+    @pytest.mark.complete(
+        "ip monitor ",
+        require_cmd=True,
+        skipif="ip monitor help 2>/dev/null; (( $? != 255 ))",
+    )
+    def test_monitor(self, completion):
+        assert "neigh" in completion
+        assert "all" in completion
+
     @pytest.mark.complete("ip -", require_cmd=True)
     def test_options(self, completion):
         assert "-family" in completion