path/filepath: clean up a triple negative.

also make the error prints better in the test.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4556069

src/pkg/path/filepath/match.go

@@ -124,9 +124,8 @@ func matchChunk(chunk, s string) (rest string, ok bool, err os.Error) {
 			s = s[n:]
 			chunk = chunk[1:]
 			// possibly negated
-			notNegated := true
-			if len(chunk) > 0 && chunk[0] == '^' {
-				notNegated = false
+			negated := chunk[0] == '^'
+			if negated {
 				chunk = chunk[1:]
 			}
 			// parse all ranges
@@ -152,7 +151,7 @@ func matchChunk(chunk, s string) (rest string, ok bool, err os.Error) {
 				}
 				nrange++
 			}
-			if match != notNegated {
+			if match == negated {
 				return
 			}
 

src/pkg/path/filepath/match_test.go

@@ -69,6 +69,13 @@ var matchTests = []MatchTest{
 	{"*x", "xxx", true, nil},
 }
 
+func errp(e os.Error) string {
+	if e == nil {
+		return "<nil>"
+	}
+	return e.String()
+}
+
 func TestMatch(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		// XXX: Don't pass for windows.
@@ -77,7 +84,7 @@ func TestMatch(t *testing.T) {
 	for _, tt := range matchTests {
 		ok, err := Match(tt.pattern, tt.s)
 		if ok != tt.match || err != tt.err {
-			t.Errorf("Match(%#q, %#q) = %v, %v want %v, nil", tt.pattern, tt.s, ok, err, tt.match)
+			t.Errorf("Match(%#q, %#q) = %v, %q want %v, %q", tt.pattern, tt.s, ok, errp(err), tt.match, errp(tt.err))
 		}
 	}
 }