cmd/geth: added 'geth bug' command (#3684)

* cmd/geth: added 'geth bug' command

Added bug command to geth, which will open a browser window
with an issue template and some additional system information.

* cmd/geth: update bug with better infos

* cmd/geth: added browser fallback

* cmd/geth: govet yo momma

cmd/internal/browser/browser.go

@@ -0,0 +1,46 @@
+// Copyright 2016 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.
+
+// Package browser provides utilities for interacting with users' browsers.
+package browser
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+)
+
+// Commands returns a list of possible commands to use to open a url.
+func Commands() [][]string {
+	var cmds [][]string
+	if exe := os.Getenv("BROWSER"); exe != "" {
+		cmds = append(cmds, []string{exe})
+	}
+	switch runtime.GOOS {
+	case "darwin":
+		cmds = append(cmds, []string{"/usr/bin/open"})
+	case "windows":
+		cmds = append(cmds, []string{"cmd", "/c", "start"})
+	default:
+		cmds = append(cmds, []string{"xdg-open"})
+	}
+	cmds = append(cmds,
+		[]string{"chrome"},
+		[]string{"google-chrome"},
+		[]string{"chromium"},
+		[]string{"firefox"},
+	)
+	return cmds
+}
+
+// Open tries to open url in a browser and reports whether it succeeded.
+func Open(url string) bool {
+	for _, args := range Commands() {
+		cmd := exec.Command(args[0], append(args[1:], url)...)
+		if cmd.Start() == nil {
+			return true
+		}
+	}
+	return false
+}