ebnflint: better handling of stdin

- don't rely on /dev/stdin as the name for standard input
- employ EBNF extraction if the source contains tags

"cat source.html | ebnflint" works now

R=r
CC=golang-dev
https://golang.org/cl/4641075

src/cmd/ebnflint/ebnflint.go

@@ -35,6 +35,12 @@ var (
 )
 
 
+func report(err os.Error) {
+	scanner.PrintError(os.Stderr, err)
+	os.Exit(1)
+}
+
+
 func extractEBNF(src []byte) []byte {
 	var buf bytes.Buffer
 
@@ -75,34 +81,35 @@ func extractEBNF(src []byte) []byte {
 func main() {
 	flag.Parse()
 
-	var filename string
+	var (
+		filename string
+		src      []byte
+		err      os.Error
+	)
 	switch flag.NArg() {
 	case 0:
-		filename = "/dev/stdin"
+		filename = "<stdin>"
+		src, err = ioutil.ReadAll(os.Stdin)
 	case 1:
 		filename = flag.Arg(0)
+		src, err = ioutil.ReadFile(filename)
 	default:
 		usage()
 	}
-
-	src, err := ioutil.ReadFile(filename)
 	if err != nil {
-		scanner.PrintError(os.Stderr, err)
-		os.Exit(1)
+		report(err)
 	}
 
-	if filepath.Ext(filename) == ".html" {
+	if filepath.Ext(filename) == ".html" || bytes.Index(src, open) >= 0 {
 		src = extractEBNF(src)
 	}
 
 	grammar, err := ebnf.Parse(fset, filename, src)
 	if err != nil {
-		scanner.PrintError(os.Stderr, err)
-		os.Exit(1)
+		report(err)
 	}
 
 	if err = ebnf.Verify(fset, grammar, *start); err != nil {
-		scanner.PrintError(os.Stderr, err)
-		os.Exit(1)
+		report(err)
 	}
 }