cmd/go-contrib-init: add start of new tool to help new Go contributors

Updates golang/go#17802

Change-Id: Ieb4be41039d414a3ba6766d98ed95a6154f964f4
Reviewed-on: https://go-review.googlesource.com/45078
Reviewed-by: Steve Francia <spf@golang.org>

cmd/go-contrib-init/contrib.go

@@ -0,0 +1,83 @@
+// Copyright 2017 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.
+
+// The go-contrib-init command helps new Go contributors get their development
+// environment set up for the Go contribution process.
+//
+// It aims to be a complement or alternative to https://golang.org/doc/contribute.html.
+package main
+
+import (
+	"bytes"
+	"flag"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+var repo = flag.String("repo", "go", "Which go repo you want to contribute to. Use \"go\" for the core, or e.g. \"net\" for golang.org/x/net/*")
+
+func main() {
+	log.SetFlags(0)
+	flag.Parse()
+
+	checkCLA()
+	checkGoroot()
+	checkWorkingDir()
+}
+
+func checkCLA() {
+	slurp, err := ioutil.ReadFile(cookiesFile())
+	if err != nil && !os.IsNotExist(err) {
+		log.Fatal(err)
+	}
+	if bytes.Contains(slurp, []byte("go.googlesource.com")) &&
+		bytes.Contains(slurp, []byte("go-review.googlesource.com")) {
+		// Probably good.
+		return
+	}
+	log.Fatal("Your .gitcookies file isn't configured.\n" +
+		"Next steps:\n" +
+		"  * Submit a CLA (https://golang.org/doc/contribute.html#cla) if not done\n" +
+		"  * Go to https://go.googlesource.com/ and click \"Generate Password\" at the top,\n" +
+		"    then follow instructions.\n" +
+		"  * Run go-contrib-init again.\n")
+}
+
+func cookiesFile() string {
+	if runtime.GOOS == "windows" {
+		return filepath.Join(os.Getenv("USERPROFILE"), ".gitcookies")
+	}
+	return filepath.Join(os.Getenv("HOME"), ".gitcookies")
+}
+
+func checkGoroot() {
+	v := os.Getenv("GOROOT")
+	if v == "" {
+		return
+	}
+	if *repo == "go" {
+		if strings.HasPrefix(v, "/usr/") {
+			log.Fatalf("Your GOROOT environment variable is set to %q\n"+
+				"This is almost certainly not what you want. Either unset\n"+
+				"your GOROOT or set it to the path of your development version\n"+
+				"of Go.", v)
+		}
+		slurp, err := ioutil.ReadFile(filepath.Join(v, "VERSION"))
+		if err == nil {
+			slurp = bytes.TrimSpace(slurp)
+			log.Fatalf("Your GOROOT environment variable is set to %q\n"+
+				"But that path is to a binary release of Go, with VERSION file %q.\n"+
+				"You should hack on Go in a fresh checkout of Go. Fix or unset your GOROOT.\n",
+				v, slurp)
+		}
+	}
+}
+
+func checkWorkingDir() {
+	// TODO
+}