filters: handle presence syntax correctly

Signed-off-by: Stephen J Day <stephen.day@docker.com>

filters/filter_test.go

@@ -112,6 +112,15 @@ func TestFilters(t *testing.T) {
 				corpus[8],
 			},
 		},
+		{
+			name:  "NameAndLabelPresent",
+			input: "labels.foo,name",
+			expected: []interface{}{
+				corpus[0],
+				corpus[2],
+				corpus[8],
+			},
+		},
 		{
 			name:  "LabelValue",
 			input: "labels.foo==true",

filters/parser.go

@@ -99,7 +99,7 @@ func (p *parser) selector() (selector, error) {
 	}
 
 	switch p.scanner.peek() {
-	case tokenSeparator, tokenEOF:
+	case ',', tokenSeparator, tokenEOF:
 		return selector{
 			fieldpath: fieldpath,
 			operator:  operatorPresent,