build: force all Windows batch files to CRLF

Batch files should use CRLF endings. LF endings mostly
work but in some situations they cause random errors like
goto commands failing for mysterious reasons. See
golang.org/issue/37791 for more information.

Next CL triggered one of such bug (a label was not being
recognized), so prepare for it by converting to CRLF.

This CL also touches all existing batch files to force git
to update the line endings (unfortunately, changing
.gitattributes only has effect next time the file is checked
out or modified).

Fixes #37791
Updates #9281

Change-Id: I6f9a114351cb7ac9881914400aa210c930eb8cc1
Reviewed-on: https://go-review.googlesource.com/c/go/+/96495
Run-TryBot: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

.gitattributes

@@ -8,3 +8,9 @@
 # See golang.org/issue/9281
 
 * -text
+
+# The only exception is Windows files that must absolutely be CRLF or
+# might not work. Batch files are known to have multiple bugs when run
+# with LF endings. See golang.org/issue/37791 for more information.
+
+*.bat text eol=crlf

src/all.bat

@@ -1,6 +1,7 @@
 :: Copyright 2012 The Go Authors. All rights reserved.
 :: Use of this source code is governed by a BSD-style
 :: license that can be found in the LICENSE file.
+
 @echo off
 
 setlocal

src/clean.bat

@@ -1,6 +1,7 @@
 :: Copyright 2012 The Go Authors. All rights reserved.
 :: Use of this source code is governed by a BSD-style
 :: license that can be found in the LICENSE file.
+
 @echo off
 
 setlocal

src/make.bat

@@ -132,3 +132,4 @@ set GOBUILDFAIL=1
 if x%GOBUILDEXIT%==x1 exit %GOBUILDFAIL%
 
 :end
+

src/race.bat

@@ -49,4 +49,3 @@ echo All tests passed.
 
 :end
 if x%GOBUILDEXIT%==x1 exit %GOBUILDFAIL%
-

src/run.bat

@@ -1,6 +1,7 @@
 :: Copyright 2012 The Go Authors. All rights reserved.
 :: Use of this source code is governed by a BSD-style
 :: license that can be found in the LICENSE file.
+
 @echo off
 
 :: Keep environment variables within this script

test/winbatch.go

@@ -0,0 +1,30 @@
+// run
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check that batch files are maintained as CRLF files (consistent behaviour
+// on all operating systems). See https://github.com/golang/go/issues/37791
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+func main() {
+	batches, _ := filepath.Glob(runtime.GOROOT() + "/src/*.bat")
+	for _, bat := range batches {
+		body, _ := ioutil.ReadFile(bat)
+		if !bytes.Contains(body, []byte("\r\n")) {
+			fmt.Printf("Windows batch file %s does not contain CRLF line termination.\nTry running git checkout src/*.bat to fix this.\n", bat)
+			os.Exit(1)
+		}
+	}
+}