Added a small utility method to display warnings when parsing command arguments. (#16441)

* Added a small utility method to display warnings when parsing command arguments

Will print warning if flag is passed after arguments e.g.
vault <command> -a b -c
In this example -c will be interpreted as an argument which may be misleading

command/base_helpers_test.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -209,3 +210,48 @@ func TestParseFlagFile(t *testing.T) {
 		})
 	}
 }
+
+func TestArgWarnings(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		args     []string
+		expected string
+	}{
+		{
+			[]string{"a", "b", "c"},
+			"",
+		},
+		{
+			[]string{"a", "-b"},
+			"-b",
+		},
+		{
+			[]string{"a", "--b"},
+			"--b",
+		},
+		{
+			[]string{"a-b", "-c"},
+			"-c",
+		},
+		{
+			[]string{"a", "-b-c"},
+			"-b-c",
+		},
+		{
+			[]string{"-a", "b"},
+			"-a",
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+
+		t.Run(tc.expected, func(t *testing.T) {
+			warnings := generateFlagWarnings(tc.args)
+			if !strings.Contains(warnings, tc.expected) {
+				t.Fatalf("expected %s to contain %s", warnings, tc.expected)
+			}
+		})
+	}
+}