cmd/go: split out cmd/go/internal/env

This is one CL in a long sequence of changes to break up the
go command from one package into a plausible group of packages.

This sequence is concerned only with moving code, not changing
or cleaning up code. There will still be more cleanup after this sequence.

The entire sequence will be submitted together: it is not a goal
for the tree to build at every step.

For #18653.

Change-Id: I28b20d53d20dff06eede574eb5c20359db0d3991
Reviewed-on: https://go-review.googlesource.com/36200Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/go/bug.go

@@ -18,6 +18,7 @@ import (
 
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
+	envcmd "cmd/go/internal/env"
 )
 
 var cmdBug = &base.Command{
@@ -42,7 +43,7 @@ func runBug(cmd *base.Command, args []string) {
 	fmt.Fprintln(&buf, "```")
 	fmt.Fprintf(&buf, "go version %s %s/%s\n", runtime.Version(), runtime.GOOS, runtime.GOARCH)
 	env := cfg.NewEnv
-	env = append(env, extraEnvVars()...)
+	env = append(env, envcmd.ExtraEnvVars()...)
 	for _, e := range env {
 		// Hide the TERM environment variable from "go bug".
 		// See issue #18128

src/cmd/go/env.go → src/cmd/go/internal/env/env.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package main
+package env
 
 import (
 	"fmt"
@@ -16,7 +16,7 @@ import (
 	"cmd/go/internal/work"
 )
 
-var cmdEnv = &base.Command{
+var CmdEnv = &base.Command{
 	Run:       runEnv,
 	UsageLine: "env [var ...]",
 	Short:     "print Go environment information",
@@ -30,7 +30,7 @@ each named variable on its own line.
 	`,
 }
 
-func mkEnv() []cfg.EnvVar {
+func MkEnv() []cfg.EnvVar {
 	var b work.Builder
 	b.Init()
 
@@ -87,8 +87,8 @@ func findEnv(env []cfg.EnvVar, name string) string {
 	return ""
 }
 
-// extraEnvVars returns environment variables that should not leak into child processes.
-func extraEnvVars() []cfg.EnvVar {
+// ExtraEnvVars returns environment variables that should not leak into child processes.
+func ExtraEnvVars() []cfg.EnvVar {
 	var b work.Builder
 	b.Init()
 	cppflags, cflags, cxxflags, fflags, ldflags := b.CFlags(&load.Package{})
@@ -104,7 +104,7 @@ func extraEnvVars() []cfg.EnvVar {
 
 func runEnv(cmd *base.Command, args []string) {
 	env := cfg.NewEnv
-	env = append(env, extraEnvVars()...)
+	env = append(env, ExtraEnvVars()...)
 	if len(args) > 0 {
 		for _, name := range args {
 			fmt.Printf("%s\n", findEnv(env, name))

src/cmd/go/main.go

@@ -15,6 +15,7 @@ import (
 
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
+	"cmd/go/internal/env"
 	fmtcmd "cmd/go/internal/fmt"
 	"cmd/go/internal/help"
 	"cmd/go/internal/test"
@@ -26,7 +27,7 @@ func init() {
 		work.CmdBuild,
 		cmdClean,
 		cmdDoc,
-		cmdEnv,
+		env.CmdEnv,
 		cmdBug,
 		cmdFix,
 		fmtcmd.CmdFmt,
@@ -100,7 +101,7 @@ func main() {
 	// but in practice there might be skew
 	// This makes sure we all agree.
 	cfg.OrigEnv = os.Environ()
-	cfg.NewEnv = mkEnv()
+	cfg.NewEnv = env.MkEnv()
 	for _, env := range cfg.NewEnv {
 		if os.Getenv(env.Name) != env.Value {
 			os.Setenv(env.Name, env.Value)