maintner: update TestLineValue to use new lineValueOK

In CL 152779, lineValue was modified to return just the value,
lineValueRest was added to do the same task as the old lineValue,
and a new lineValueOK with a third bool return value was created.

This change fixes a test build failure by adapting TestLineValue to
use the new lineValueOK function, and renaming it to TestLineValueOK.
Also add two test cases to cover the new bool return value.

Updates golang/go#28318

Change-Id: I08106cc14f0c418a880ab139310830943a3a1ad9
Reviewed-on: https://go-review.googlesource.com/c/153441
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

maintner/gerrit_test.go

@@ -243,54 +243,78 @@ func TestSubject(t *testing.T) {
 	}
 }
 
-func TestLineValue(t *testing.T) {
+func TestLineValueOK(t *testing.T) {
 	tests := []struct {
 		all, prefix, want, wantRest string
+		wantOK                      bool
 	}{
 		{
 			all:      "foo:  value ",
 			prefix:   "foo:",
 			want:     "value",
 			wantRest: "",
+			wantOK:   true,
 		},
 		{
 			all:      "foo:  value\n",
 			prefix:   "foo:",
 			want:     "value",
 			wantRest: "",
+			wantOK:   true,
+		},
+		{
+			all:      "foo:\n",
+			prefix:   "foo:",
+			want:     "",
+			wantRest: "",
+			wantOK:   true,
+		},
+		{
+			all:      "bar:\n",
+			prefix:   "foo:",
+			want:     "",
+			wantRest: "",
+			wantOK:   false,
 		},
 		{
 			all:      "bar: other\nfoo:  value\n",
 			prefix:   "foo:",
 			want:     "value",
 			wantRest: "",
+			wantOK:   true,
 		},
 		{
 			all:      "notfoo: other\nfoo:  value\n",
 			prefix:   "foo:",
 			want:     "value",
 			wantRest: "",
+			wantOK:   true,
 		},
 		{
 			all:      "Foo: bar\nLabel: Vote=+1\nLabel: Vote=+2\n",
 			prefix:   "Label: ",
 			want:     "Vote=+1",
 			wantRest: "Label: Vote=+2\n",
+			wantOK:   true,
 		},
 		{
 			all:      "Label: Vote=+2\n",
 			prefix:   "Label: ",
 			want:     "Vote=+2",
 			wantRest: "",
+			wantOK:   true,
 		},
 	}
 	for _, tt := range tests {
-		got, gotRest := lineValue(tt.all, tt.prefix)
+		got, gotRest, gotOK := lineValueOK(tt.all, tt.prefix)
 		if got != tt.want {
-			t.Errorf("lineValue(%q, %q) returned value %q; want %q", tt.all, tt.prefix, got, tt.want)
+			t.Errorf("lineValueOK(%q, %q) returned value %q; want %q", tt.all, tt.prefix, got, tt.want)
 		}
 		if gotRest != tt.wantRest {
-			t.Errorf("lineValue(%q, %q) returned rest %q; want %q", tt.all, tt.prefix, gotRest, tt.wantRest)
+			t.Errorf("lineValueOK(%q, %q) returned rest %q; want %q", tt.all, tt.prefix, gotRest, tt.wantRest)
+		}
+		if gotOK != tt.wantOK {
+			t.Errorf("lineValueOK(%q, %q) returned ok %v; want %v", tt.all, tt.prefix, gotOK, tt.wantOK)
 		}
 	}
 }