test: add cmpout to testlib

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5699060

test/deferprint.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2010 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/fixedbugs/bug328.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/fixedbugs/bug409.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2012 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/goprint.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/helloworld.go

-// $G $F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/ken/cplx0.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/ken/string.go

-// $G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/printbig.go

-// $G $F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+// cmpout
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/run.go

@@ -238,6 +238,9 @@ func (t *test) run() {
 	action = strings.TrimSpace(action)
 
 	switch action {
+	case "cmpout":
+		action = "run" // the run case already looks for <dir>/<test>.out files
+		fallthrough
 	case "compile", "build", "run", "errorcheck":
 		t.action = action
 	default:

test/testlib

@@ -17,6 +17,10 @@ run() {
 	$G $D/$F.go && $L $F.$A && ./$A.out "$@"
 }
 
+cmpout() {
+	$G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out
+}
+
 errorcheck() {
 	errchk $G -e $D/$F.go
 }